I would like to pay for access to a porn site, but every time I visit
one, I'm afraid that it's a scam and my credit card will show up with
all kinds of fraudulent charges if I hand over the number.  If you
look up "porn site reviews" or something like that on google, you can
find plenty of sites, but I have no idea whether those sites are just
scams run by people with fraudulent porn sites either.

Obviously, web porn is not something they review in Consumer Reports. 
So what I'm looking for is one or more sites that review for-pay
erotica websites and that are actually themselves reputable in some
way.  Or, failing that, a sure method of avoiding problems like
unauthorized charges.  (I do know that you are not "really" liable for
unauthorized credit card charges, but I'd rather not go through the
hassle, and there's always a danger that I wouldn't notice too.)  By
"sure method," I mean that maybe there is a centralized billing system
that is very reputable and many porn sites subscribe to it.

Please be careful in your answer - if I wanted a hodge-podge of easy
results from a google search, I could do it myself :-)

I think your best bet is to go after the unauthorized charge problem
from the credit card side rather than trying to find an arbiter of
whether or not a particular website is fraudulent.  Domain names,
especially those associated with porn, frequently change owners
without notice, making such a list very difficult to maintain. 
Furthermore, even a legitimate site could be hacked and your credit
card number could be stolen and misused.

The approach I recommend, which I use personally for all of my
Internet transactions, is to get a credit card that allows you to
generate Virtual Account Numbers.  Several banks include this as a
free feature, including Citigroup.  You either download software to
your computer or use a Web-based version of the software to generate a
unique credit card number for each of your transactions.  You can
limit the amount that can be charged to that number and set the
expiration date for as little as one month.

Once the merchant charges that account number, no one else except that
merchant can charge that account number.  Furthermore, once the
merchant has charged the limit associated with that account number,
they cannot charge anymore.  This also prevents you from being stuck
with automatic recurring charges when you do not want them if you have
set the limit to an amount that only allows for one month.

A strategy you could use: to begin with, you could purchase each month
of service with a unique account number set for the amount of the
purchase rounded up to the nearest dollar.  If you gain confidence in
the merchant and desire an automatic recurring charge program, you can
give the merchant a new account number each year that is good for the
total of the monthly charges for that year rounded up to the nearest
dollar.

"Virtual I.D." PC Magazine (August, 2002)
http://www.findarticles.com/p/articles/mi_zdpcm/is_200208/ai_ziff29603

Sincerely,

Wonko

I cannot post a link to this site because of its adult content, but
"Sir Rodney's Guide to Online Erotica" may be of use to you. Sirrodney
dot com.

A site named 89 dot com gives links to free "adult content", where you
can get an eyeful, but maybe only for 30 sec. previews.