I had this thought a while back and gave it a try. I have an i5-3210M in a laptop. The GPU is capable of 11.5 MH/s with BFGminer and 2 GPU threads (BTC mining). The 3210M is dual core with hyperthreading, and the GPU mining will eat up one "core". You can get another ~8 MH/s out of the remaining cores. I don't remember the miner I used for CPU... it was like cpu-pooler-miner or something. With both CPU and GPU mining, it uses 24 Watts.
Thanks, so the intel's integrated GPU is very comparative with AMD's Fusion GPU but AMD's has 100-300 stream processors, which means that Intel has the capability to make a nice discrete GPU but they hasn't made one.
