On one bike I have a rack with rectangular bag made by Jandd. This holds about the same amount as my Deuter backpack which I use with my road bike. The Deuter is nice because it has a frame suspension which allows more air to circulate between you and the pack. I have a Camelbak that I have yet to use.

I won't bother to tell what I carry as I'm pretty much an unprepared Newbie and have yet to learn basic repair skills (which I expect to start the end of March). I mostly commute to work so I sometimes carry clothes and food. If I ever needed to carry heavy or large amounts of gear, I would definitely go with panniers.

Carole

PS - Good thread!