I just bought a Hitachi HTS725050A9A364 for my 5310m notebook (500GB 7200RPM 16MB). It's a blazing fast drive; I have one in my 5310m at present, testing it for StorageReview.
I picked it up for - get this - $96 shipped from TD (
http://tinyurl.com/yfmt5zn) but there's a $15 MIRC so it's actually $81 for the fastest notebook HDD on the market!