Recently I've been upgrading my bike. I've put a very lovely Selle Italia Flite on it, 2Ti Eggbeaters, Avid Juicy Carbons (Found them for $100 each!) and a Speedball on it. I still have $500 left for it though. The guys at the LBS didn't give any helpful hints on what to buy next. Prove your worthiness, BF's!
Things That Don't Need Any Upgrading:
Pedals
Seat
Seatpost
Tires
Wheelset
Rear Shock
Brakes
So, I'm thinking cassette (rotational mass), the controls or maybe components.
Oh, it's a Trek Fuel Ex7, so it's mostly Deore components.