take a look at mine (link on my sig) and get some ideas.
To add to what has been said, I would start with the wheels and tires, get custom made clinchers (easy at 1250g range) and Veloflex RC or Vittoria CE tires or, if you don't mind tubulars you can go with edge rims, sapim cx-ray spokes and extralite or Tune hubs with Veloflex extreme tires. That will definitely save you about 600-800g (1.5-2lbs). A Recon 10speed alu cassette will save you another 100g and shifts very well on Campy 10speed.
As for the brakes, I went through the same dilemma not too long ago and, after testing many brands, I ended with Feather Brakes (199g with pads and holders). The problem is they don;t make them anymore (the original style at least) but you may find them at fleabay every now and then. Another good choice are also the KCNC C7 or the EE Brakes.
Bar and stem can be swapped for lighter components like Edge Composites stem and bar which can be found cheap as EDGE changed their name to ENVE and all items labeled with EDGE logo are on closeout. Use a KMC X10SL chain instead and will save you some grams and better shifting as well. And last is the saddle, I know SMP's are comfy but also heavy. The SMP Plus comes in at 360g (claimed) and there are several comparable saddles in the market that will save you about 200g.