Had to search the site for literally 30 minutes lol... finally found it in Deals, then scrolled down to a big banner for Prime, and was able to sign up on the following page.

Used to be MUCH MUCH easier you guys had a simple advert buy on the home page. Guarantee you're going to be losing some $$ on that if you hide the Prime sign up so well. I know from years of running subscription websites you want it to be so easy and so noticeable people will literally trip over it :D

I'd recommend an animated PRIME STATUS button or something like, that shows up after you log in.