Here's the howto for the 15 inch 2009 MacBook Pro:
http://www.ifixit.com/Guide/Repair/Insta...lacement/1715/1

Another option is to put an SSD in place of the optical drive, leaving the stock HDD in place. I'm considering going this route, as the optical drive is near useless to me these days. MCE sells a mounting kit that includes an enclosure to make the internal optical drive an external USB one instead.
http://www.mcetech.com/optibay/

I've never seen Apple sell the SSDs standalone, but from what I understand, they source theirs from Toshiba.