I'm looking for information on buying a diamond ring, and I'm hoping
to use the Internet as a research tool.  What are the best sites to go
to, and are there any caveats?

Hi seekingone-ga,
I must say that it's a very interesting question and there can be lot
and lot of answers but the whole thing is that what exactly you are
looking for in a Diamond. I recently purchased a Diamond ring and I
researched for around ten days in various sites and various shops and
the summary of all my finding is that it all depends on your budget
and 4C's of Diamond.
By 4C, I mean Color, Clarity, Cut and Carat. Price of a diamond will
depend on all these four and not on a single quality.
To check out more on this, visit this site:
http://www.jewelrymall.com/diamond-guide.html

Along with the 4Cs, there is one more C and that is Cost. I will
suggest, that when you are buying the diamond, make sure that it's
from a genuine source. Certified diamonds will be more costly than a
non-certified diamond.

This site has a full checklist for buying a diamond.
http://www.diamondgrading.com/Articles_How_To_Buy_A_Diamond.htm

Following site will give you an insight about Diamond FAQ, and it has
a Tutorial on Diamond.
http://www.mysimon.com/guides/index.jhtml?pgid=wedding&cid=advisor_ring

Here is one more tutorial on Diamonds:
http://www.diamondreview.com/tutor/4cs/tutor_4cs_intro.shtml

Almost all the sites will talk about the 4Cs. But how to check about
the color, clarity and other quality in a diamond.
Here is one site which gives information about how you can find the
details about 4Cs of diamond:
http://www.diamondcutters.com/tutorial.html

This site, particularly helped me a lot in finalizing my decision
about the diamond ring. It, like other sites, gives you detail about
4Cs, but also speaks about what should be taken care while purchasing
it over the internet, which are the recommended diamond sites, Do's
and dont's for purchasing a diamond, how the payment should be made
and so on.
http://www.bridaltips.com/diamond.htm

One more site gives a Step by Step guide for purchasing a diamond.
http://www.wedalert.com/content/articles/how_to_buy_a_diamond.shtml

To find out the difference between the certified and the non certified
diamond, here is a link:
http://www.mondera.com/learn/FAQDiamond.asp

About cavets, check this site too:
http://www.maca.gov.nt.ca/consaffairs/purchase/diamond_ring.html

Search stings used: buy diamond ring
://www.google.com/search?q=buy+diamond+ring&hl=en

In the last I'd like to say that the more time you'll spend in
investigating about this, the more you'll get confused. Believe me,
after 10 days, I thought of opening a diamond consultancy :) I got
some much confused that in every ring, I either disliked the color, or
any other C.. ;-)

I hope this will definitely help you in finding the best deal with the
best diamond for you.

Regards,
netcrazy-ga

http://www.adiamondisforever.com/ is full of great information too.

I recently bought a diamond engagement ring, so I can empathize with
the comment "In the last I'd like to say that the more time you'll
spend in
investigating about this, the more you'll get confused. Believe me,
after 10 days, I thought of opening a diamond consultancy."  I did
too.

Info on the net helped educate me as a diamond buyer (the 4 C's,
pricing, etc)but the real work started once I got the jeweller.  The
number one thing I can add to the answer above is that **picking a
diamond is a subjective process**.  Don't pick a diamond based solely
on the hard specs.  So what if it's an E coloured diamond, ideal cut,
VSI clarity?  Even within those specs there's a range of appearance. 
I must have driven my jeweller crazy with the number of times she
brought in diamonds to my specifications and I sent them back because
I was picky about how they looked.  Eventually I found one (and
remember, they all had the same specs) that looked that little bit
nicer.  And I bought it.  And it was a hit when I presented it to my
girlfriend.

As a rough guide, I followed
http://www.soyouwanna.com/site/syws/ring/ring.html

One other thing: depending on how socially conscious you are you might
consider buying a diamong with a laser-engraved serial number on it. 
This confirms which mine the diamond came from.  The diamond industry
is having major problems with illegal diamonds coming from mines which
are operated by slaves in third world countries.  The phrase you might
have heard is "blood diamonds" or "conflict diamonds."  Not all
legitimate mines are engraving diamonds yet -- most are moving towards
it -- but you can be ahead of the curve and demand it from your
jeweller.  The diamond I bought came from Canada.  As a bonus you get
the peace of mind that your diamond is marked, so you can be assured
when you send the ring out for periodic cleaning that you get the same
diamond back again.

I worked my way through college selling jewelry at a department store.
 I learned some very important things about diamond buying:  As
mentioned above, every diamond is different, even if they have the
exact same specs.  A diamond may only have a single inclusion (flaw),
but if that inclusion is a black spot right on top of the diamond,
your fiancee will notice it (and if she's obsessive like me, it will
bug her every day).  It is so important to look at each individual
ring you are considering, both with and without the jewelers loupe
(ALWAYS ask to use the loupe -- hold the loupe to your eye, and bring
the diamond up to it).  If you are inexperienced at diamond buying and
don't want to know absolutely everything about the 4 C's, you will end
up with a nice ring if you examine it and it looks white instead of
yellowish (D-F is colorless, and the difference in price for a
colorless diamond is usually negligible), it sparkles and you can see
rainbow colors in it, and you don't see any black or white spots or
cloudiness without the loupe (be sure to look into the diamond; a bad
cut can cause an inclusion to reflect multiple times, in all of the
facets) and you don't see any inclusions you can't live using the
loupe (there WILL be inclusions, but the diamond shouldn't look cloudy
or dark, and sometimes a inclusion you notice with the loupe then
becomes visible to you with the naked eye -- in any case, I wouldn't
advise a diamond below I1, but some individual diamonds are quite nice
looking even at I1).  INSIST on a certified diamond, but remember that
the inflated appraised value on the certificate is for insurance
purposes.  :)  (Also insist that the diamond be tested in front of you
before you purchase it.)  A couple of words on price as well: the ring
is, after all, just rocks and metal, and each stone is unique, so
unless you or your fiancee have a specific jewelry store preference,
you should check the fine jewelry department at your favorite
department store (I will add that my wedding ring came from a jeweler
and my anniversary band came from a department store, and the
department store has a much better lifetime guarantee (which was free)
than the jeweler's (which I had to pay extra for).  Another tip: if
you buy a diamond that is slightly under a "standard" weight (1/2
carat, 1 carat, etc.), you will get a better price, because the price
jumps as you hit each weight.  You will also get a better price if you
choose a ring with a smaller center stone complimented by side stones
as opposed to a ring with a single large stone (again, you're paying
more as you hit each higher carat weight) -- and oddly enough, when
women shop with their fiances, these are usually the rings they choose
for themselves!  You will pay less for 10 karat gold, but anything
below 14 karat gold will tarnish if not worn daily (Hopefully she'll
be wearing it daily!).  White gold becomes a little brownish over time
(a plating is applied to white gold which eventually wears off --
replating is usually not covered under warranty), while platinum does
not.  Finally, always ask about special ordering.  At the store where
I worked, special orders tended to be set with better stones than the
same rings in the display case (not sure if this is true everywhere). 
And if a ring is not exactly what you had in mind, ask about a special
order.  Most rings can be ordered with a larger or smaller center
stone, and sometimes the price difference to upgrade is not as great
for a special order as it is for rings that are on display with
different-sized stones.  And if you do special order and don't like
what you see, send it back and try again!  I could say much more on
the subject (I love diamonds, and I've had wonderful experiences
buying and selling them), but I'll content myself with saying good
luck with your purchase, and congratulations!

pricescope.com

This website has stacks of info,
Good helpful forum
www.diamonds-diamonds.info
 
and it is unbiased

Actually, www.diamonds-diamonds.info isn't as unbiased as one might
hope.  Several hidden agendas are at work there.

go to a jewelry store and decide what weight, color, and quality you
want--it helped me to actually *see* the stones; and then go to
pricescope.com and match it to the what you wanted at the local store.
the local store wanted $33,000 for the one i bought for my financee
and i got mine from pricescope, the exact same diamond specs for
$11,000... i (we) couldn't be happier...