the maxtor diamondmax 10 series is tops right now in terms of holistic bang for the buck: speed, size, acoustics. the western digital raptor wd740gd is faster, but it tops out at 74gb and commands a much higher price per gigabyte. most power users should still be pleased with the dm10, that's what i would recommend for you.
www.zipzoomfly.com is a great vendor for hard drives, they pack them better than most and that means a lot in terms of reliability. prices are also reasonable to good on most other things and 2-day shipping is priced in. brutish packing/shipping can often result in doa drives, or at least drives with shorter lifespans.
www.newegg.com is widely regarded as the top general vendor for computer stuff.