I commute regularily, however due to what I have to carry its either 3 or 4 days a week and the other day/week I use to carry in fresh office clothing as required.
My commuter was built up from a bare frame.
Pic is out of date as the bike now has:-
X0 twist shifter (lighter and less cluttered looking than shimano levers which are now on my daughters commuter (7 speed converted to 8 using a 9speed cassette))
Foam grips (Avenir, similar to KCNC or Pork rinds) my Giant lock on grips are now on the daughters commuter
X9 rear mech (lighter than the LX which is now on the wifes bike)
ITM seatpost (lighter and the carbon post is now on my MTB)
Front and rear levers swapped side to side (continental style) to shorten cable runs (lighter)
Alligator discs front and rear (lighter the old discs are on my younger daughters MTB)
IS mount front calliper (lighter, the old calliper is now being held as a spare)
Downtube guard/rear mudguard removed for summer
Stem flipped and one headset spacer replaced with 10mm ILO 15mm to lower the bars slightly.
Total weight without rack and guards is just over 10Kg, total cost is £350 so far through judicious ebay/classified buying.
Simon