I used to ride every day for school in LA. Definitely second the panniers and rack, you can do errands and grocery shopping with them. I like handlebar mirrors, less fiddly and geeky than helmet mirrors.
ALso second the flashing LED lights, red for the rear, white for the front. I like the cateye ones that form a beam, aim them for car driver height, they're to let them see you, not for you to see the ground. For that, a car foglight hooked to a sealed lead acid battery works well. Anything less doesn't throw a beam far enough for you to be able to avoid stuff in the road.
Also reflectorize the bike and your helmet, I hate the fluorescent yellow stickers at the bike store so i used white scotchlite from the autoparts store. It blends with the silver on the bike and helmet.
For repairs, a multitool, spare tube, patch kit and small pump, used a lot. Carried a spare brake cable, but never used. Bungie cords and 550 cord for tying stuff to the rack. ALso carried bandaids, 4x4 gauze, disinfectant and tape, these were used. Also wear gloves, the one time i didn't i spilled and messed up my palm pretty good.
If it's possible that you'll be out in the rain or before or after rain, fenders and a set of lightweight rain pants and jacket. You really need fenders otherwise the crap on the road will paint a stripe on you front and back.