Originally Posted by
tjspiel
If you have a place at work to stash shoes, a shower kit, towel, etc. that will work better in the end. By the same token I'd put the flat kit in a seat wedge or some other place on the bike itself in case you get a flat and aren't carrying the backpack.
You'll still a need a backpack, panniers or something but the less you have to carry IMHO, the better.
What he said for both the seat wedge and stashing stuff at work.
When I do use a backpack (road bike), I've been using an REI Novara pack. Works well enough. Not waterproof, but has a rain cover for when it gets wet. I've had bigger problems from a coffee thermos leaking than rain getting in - but I don't leave things that need to stay dry in the outer zippered pocket unless they're inside a heavy duty ziplok. Main compartment stays dry (except for that thermons).