Don't know what kind of camera you have so if this applies, good, if not, maybe it can help somebody else.

I use an Olympus, really like it, but it uses a proprietary battery that's expensive, $CDN40-60. Good ol' ebay has a guy selling them 2 for $US7, if I remember correctly. They work well, so when I go out I have all three batteries with me.

I get silly with the digital: once took 240 pics over a 20min modern dance presentation.