Currently in the process of acquiring parts to do this with my son. So far I have got a 14″ Giant alu-lite frame off Ebay for £9.40 and £40 on a Cane Creak headset. I already have some brakes (mixture of v-brake rear and disc front), rear XT mech, right deore shifter, Manitou forks (kindly donated from a work collegue), r ear wheel (old XT with rm20 rim, will get something light when it comes up), saddle, bars and cassette.
Need to get 165 cranks, front wheel, seatpost and 50mm 25.4mm stem, then we can start building.
Oh and some sort of chaindevice. My thinking is as he grows i will upgrade the frame and transfer old bits from my bike when I need to upgrade :wink: