You have other places like newegg.com, geeks.com, fry's and amazon. Since such things change daily as to availability you have to shop around.
My (40GB) hard drive went out on my 2003 Dell Precision M50 Laptop. I pulled it out of the laptop and found out it is a Hitachi DK23EB-40 and can be replaced with any other hard drive that is 2.5", 95mm, IDE/EIDE/parallel ATA, & is between 40-120GB.
I would like to spend as little as possible as the laptop is old, but it still works fine.
I'm not sure the best place to buy, but I do have $30 gift card at amazon.com that I need to use if they have something for a good price.