One of these things is not like the others… it’s a ripoff!
I’ve said this before, and I’ll say it again… Never buy Canon batteries. They are a rippoff. Amazon.com sells this Cannon branded battery (for my new 10D) for $46.14. They sell the generic equivalent for $12.94. I cannot tell the difference (other than one says Canon on it).
The battery for my SD300 digital elph is the same way. Amazon sells it for $34.19, but I’ve found them as cheap as $5. I’ve been using them for quite a while now and have no complaints. They perform exactly like the one that says Canon on it.
I can’t speak to other camera brands, but if your camera has an expensive battery, it may be worth your while to try the generic. You can usually find them on Amazon.