I like to write something here when I am positively surprised by an online transaction, to reward the seller beyond just the purchase price. So:
I ordered a replacement battery for my Asus laptop on Sunday night on eBay and it arrived this morning, despite it being listed as 3-4 days shipping time. It was also pretty much the cheapest option going. So if you're looking for a laptop battery, give Battery Pro a look on eBay.