Spend money on full leather gear, boots and quality gloves if you haven't already. Fuck jeans and work boots. Other than that, frame sliders, brake up grades (Lines, pads, rotors, MC etc) and lastly tools and equipment to perform your own maintenance. After buying your leathers, spend the left over money on track days. IMO all the other bolt on accessories that are marketed to make your bike faster but really don't (or that you'll never notice the gains on the street) are a waste of money.
Favorite mod so far-galfer lines. one finger stopping kicks ass
Favorite cheap mod-seat cover. Local upholstery shop has sample squares for $1, and they are just big enough to do a motorcycle seat. I change seats every few months for a new look, and not a lot of ppl have custom seats, so it stands out
Next would be the HID light conversion. It's still dark in the morning when I leave for work a big portion of the year and a good headlight is worth it's weight in gold here in deer country. You just don't realize how lacking a std. halogen bulb is until you have a HID bulb burning in there.
Spongebob brake reservoir cover. Best JuJu ever. (Knock on wood)...I haven't had a single injury in 3.5 years (since the first time I used Spongebob). The JuJu is so strong, that i won't ride without him. I bought 27 spare Spongebob's in case that one somehow comes off.
Have a few that I do,very simple but effective.
- a nice set of Michelin Power Ones
- one tooth down on the front sprocket
-adjust clutch/brake levers on clip ons up/down for a better feel
-paint the silver footpeg/passenger footpeg assemblys black to match the frame
-adjust the suspension for my fat ass
-rebuild the engine&add a big ass turbo