I want to get the highest quality 8X10 prints out of my Nikon D100. 
It takes 17MB tiff files at the highest resolution.  I am bound to
lose resolution compressing to JPG.  Is there an online site that
allows for uploading these large tiff files; or, is there a MAC
program that will convert them to an acceptable size JPG without loss
of quality?  Or, is there a common chain store that  will let me take
the large tiff files in and print from CD-rom?  I don't want to buy a
photo printer

Thanks

http://www.colormailer.com/, http://www.snapfish.com/,
http://www.shutterfly.com/, im sure those services will satisfy you. 
But you must understand a 17mb tiff file has a overkill of resolution,
it won't show on a print.  You see it looks great on screen, but the
human eye couldn't tell the difference between a high-res jpeg and a
high-res tiff, the jpeg compression technology is impressive, while it
was never intended for printing, .tiff wasn't either, or atleast not
at that resolution.  If i were you i would put it at a high-res jpeg. 
I bet you'd be more than happy with a 8x10 print from an alladin photo
print system at your local wal-mart, unlike a kodak photo print
machine, with is lower resolution, it uses the actual wal-mart
photo-lab machinery to print, great quality!

Well i hope i answered your question!