I know a lot of people who have laptops but can't use them without plugging into a power source because their batteries have failed. It kinds of defeats the purpose of having a lap top because you can't have mobile computing anymore. I know because my wife had to buy a new laptop just for this reason. The old one is working perfectly ok and all it needs is a change of batteries.
I wish I had come over to this site which has an amazing range of Laptop Batteries. They are listed under the specific laptop and notebook manufacturer and believe me, I haven't heard several of the names listed on the page.
For your information, Lowcostbatteries.com is a complete store and information site that specializes in laptop and cellular phone batteries and accessories. They do carry batteries for other electronic products such as MP3 players, digital cameras, watches and even for dog collars. They promise you top quality batteries at the lowest possible prices.