I have a ton on my Nokia 5800. My favorite is QuickMark because it has so many great features but damn, no BB version. Upcode should have a BB version but their site has been offline for a couple of days and I'm checking Kaywa now.
Edit:
Ok, get Upcode at
www.upcode.fi. It doesn't have some of the neat features of QuickMark like the ability to add contacts, but it does 1D and 2D barcodes in many more formats than I have seen supported by any other reader.
Kaywa isn't supported on BB either.