Bikes and photography are a mix made in shutter-speed-snapping heaven. Taking your bike to new and exciting places, sharing rides with friends and just seeing cool things. The biggest difficulty is actually carrying the camera in the first place!
Backpacks provide the best in terms of capacity, so if fitting your DSLR and full fleet of lenses, flashes and other accessories is top of your priority list, that is the one to choose. If you haven’t got quite so much gear (or don’t want to bring it all with you) a small, messenger style bag will sit securely on your back, just taking up less room.
For those wishing to lose weight from their back altogether, a handlebar mounted option is the way to go. These are best suited to compact cameras and SLRs as they are much smaller in size. Think more point and shoot, rather than portable studio.