MacBook white 13" - are any aftermarket batteries good?

My wife's white 13" MacBook needs a new battery and the price for an Apple branded battery is more than we want to spend if we don't have to.

Are any of the aftermarket batteries of good quality? Any recommendations for which one to buy and from what sellers?

Many thanks....

They usually are.... there are a few crowds on the internet, and many on Ebay etc.
I'm in Oz for instance, so I go for crowds who's sites are .com.au and have 12-36month warranty, and a contact that I can get a response from, rather than ebay or china related sites, where I can't be certain.
Depending on where you are, I think that is the way to go.
I think others will come along with a few recommendations, so maybe not a bad idea to post where you are, which may assist.

I'll put in another word for NewerTechology. I haven't had an opportunity to test their MacBook batteries, but they used to be a very reputable company and I've heard nothing to make me think that has changed at all.

I believe NewerTech is a part of Other World Computing (OWC). I've bought a lot of Mac products from OWC over the years and have been very happy with their products. Their MacBook battery replacement is $100 (vs. $130 from Apple). I would trust the NewerTech batt, but still have a hard time peeling $100 off for a battery. There are some available for $55 or so, which may be of comparable quality, but without hearing some user feedback I'm a bit hesitant on that. Kind of a tough decision.

FastMac has replacement batteries as well and I've seen some very good reviews. They don't use Sony cells, so that's a plus in my book.

Fastmac batteries looks like an excellent choice... but $100 is still too steep for me for a battery to go in a computer we won't be keeping all that long.

I found a seller on eBay in the USA who is selling these batteries, with 3-year warranties, like hotcakes at around $38, no tax, with free shipping yet. And the buyer reviews are excellent. So... since I won't be keeping the computer much past this year, $38 seems like a great bargain to carry the computer along for a while longer. (vs. Apple's $130!!! NOT including tax and shipping).

Thanks for the replies guys.