I was skeptical of eBay batteries, but it seems like the $45-$60 batteries on eBay do a good job. You may wish to choose one with a good warranty, pay with a credit card via PayPal, and choose a seller with good feedback. It doesn't hurt if the seller is based in the U.S.A.
For a MacBook (white or black), here are Apple's prices:
purchase a new battery: $129
*make a Genius Bar appointment or call 1-800-APL-CARE and exchange your defective battery: $99
I wanted to follow up on this thread.
I did buy a chinese battery from ebay and it's been working very well. It has about the same capacity as the original apple one, and right now it says 7 hours remaining and ive already used it for an hour (dim display, wifi off, tethered to my phone by bluetooth)
Anyway here is the battery that I bought (payed 38 CAD shipped) http://tinyurl.com/yb3s25f and if the link doesnt work anymore, i bought it from this guy: http://myworld.ebay.ca/hk-zhaoyu/
Recommended. If there are any issues, i will post them.
I just wanted to update the skeptics on the performance of the chinese battery.
As for the exterior, the little rubber foot has come off through heavy use. As far as performance goes, its still going strong, though it still incorrectly reports 77 cycles even though there are way more on it, closer to 400.
So, I must recommend this battery because of the positive experience.
Yesterday my power brick gave up and I ordered a chinese one from ebay . I expect good results