Here is my fixed gear commuter. Its a 88 or so Specialized Rock Hopper. Geared at 70 gear inches, 26x1.25" tires. Not shown are the 12.5w cygolite for night riding and my two panniers that go on the rack. It is a great solid commuter with a strong frame and wheelset. For winter its getting Freddy fenders and 26x1.9 studded tires, and a 38t ring in the front instead of the 48 that's on there now. Rear wheel is an IRO hub with a Velocity Cliff Hanger wheel, very very stout. 17t and 19t cogs.
More info at my website:
http://r2.hostrack.com/ryko/fixedgear.html
EDIT: A major mod besides going fixed was chopping down a flat bar from 22" to 19.5". Makes the bars no wider than I am which makes navigating traffic much much MUCH easier. Its also more ergonomic, since my shoulders are about that far apart. I previously had huge 24" bars on it, which in retrospect (I didn't realize it at the time) were way too wide.
