topeak 'hummer' multi-tool, park mini-chain tool (the one on the multi-tool sucks), spare 5" length of chain, 32/36mm headset wrench, spare tube, two patch kits, topeak roadmorph pump, two blue glow-sticks, spare AAA(2)/AA(3) batteries, extra rear blinky light for friends without, bag-o-change, duct tape around a pencil, a pen, and a spare D....in case I 'lose' the first one that's taped under the seat.

cellphone/keys/wallet of course.

as far as locks go, I either carry a wimpy coiled combo lock in the bag, or I wear the 5' Fahgettaboutit.