This thread is so awesome! A bunch of guys in their garages are making history and leaving world's top 500 supercomputers in the dust....
It's certainly an eye opener. I've been charting out estimated difficulty jumps, BTC exchange rates, and mHash/watt vs mHash/$ investment even more lately. If I expand much more I'm going to have to create additional circuits in my house to avoid tripping breakers.
I'm also working with some friends who have experience with growing marijuana to work on creating a more cost effective ventilation system to force the heat through my attic and then out of the house, rather than relying (mostly) on air conditioning.
And they said that stoners weren't good for anything... Ha.
I think that the level of accessibility makes this project neat. I can have a 2 year old rig push very little mining collectively or I can choose to invest in a very modern and very gpu intensive setup that will make me a somewhat competitive miner. What you may have already versus an entirely new project. Start with a little or a lot.