To the frame I've added SKS fenders, front and back, to keep the water down on rainy days. I've also added a Topeak MTX Beam Rack with quick-release for easy mounting and removal on the seat post. Paired with it is the Topeak MTX Trunk Bag for carrying all my junk. On the handlebars is a Mirrycle Big Brass Bell, a Niterider UltraFazer 3.0 headlight (coupled with a NiteRider TL 5.0 tailight on the back), and a PDA holder from Arkon Products.
I've also swapped seats, and replaced what was on there with a Selle San Marco saddle. And I put on Pedalite blinking pedals which have self-powered white, amber and red lights embedded in them, offering greater visibility to vehicles both day and night.