There are a huge range of backpacks designed for cycling that have space for a camelback bladder in them.

I use my backpack (a Vaude Splash Air 20) for both commuting to work and for my off-road adventures. I like it because it expands to take all the stuff I need to carry to work and compresses down to only hold a few tools for offroading (but that's a whole other topic...) and it means that I always have heaps of water which is readily accessible.

In terms of water storage I prefer the platypus system to the camelbacks. I've never had any problems with the platypus and find it much easier to clean than the camelback. It's also much cheaper