I commute to work and school, and plan on doing some short distance touring this summer (400 miles at most) and I need a saddlebag that will be light, spacious and waterproof, suitable for a 10 mile commute or a half loaded tour. Any suggestions? Brands? Cheap efficient Panniers?

Get the best panniers you can afford. You will thank yourself (for many reasons) later. How cheap will it really be to buy panniers again in a few years? Or when they leak on your clothes, or the seams rip, the zippers/fasteners/hangers pull out, or... the list goes on. I have Lone Peak - not the most expensive, but not cheap either. I recommend them highly.