Is this remote compatible with the Nikon D90?

I looked where it says compatabillity but i googled D90 wireless remote, and that one came up.
http://www.bennettscamera.com/spec_sheet.html?catalog[name]=Nikon-ML-L3-Infrared-Remote-Control-Nikon--&catalog[product_guids][0]=5a752ecb-3b28-42ce-8e93-08064fc44c42

Yes, that one will work perfectly.

There are much cheaper generic ones available though, like this one:
http://cgi.ebay.com/...27b7087764

They work pretty much just as well, it's just an infrared LED with a battery after all.

Or this original one, somewhat cheaper than the one that you found:
http://cgi.ebay.com/...2341wt_980

Yes it is

How about looking on Nikon's website?

http://www.nikonusa.com/...ared).html

Less than $15 at B&H Photo