Lowepro Micro Trekker 200
I've had this bag for a very short time but I like it already. It swallows my Canon EOS system with relative ease. I can pack the Elan IIe (with BP-50 grip/battery pack), EF 20/2.8, EF 50/1.4, and EF 70-200/2.8L into this small backpack. In addition, I can fit a light meter, film, wireless release, and other do-dads that I use when I go somewhere for photography. This bag is quite small but manages to hold a lot. My previous go-everywhere bag, the Lowepro Orion Trekker, was increasingly too small for the job, forcing me to place the 70-200 lens in the top compartment where it rolled freely and got banged about quite frequently.