Not come across this before but it looks interesting. Discovered it via a friend’s music Like from Facebook and seems it could be of interest to others. Closest to a “famous” act I’ve seen in the last 10min or so of flicking through is probably Younger Brother and they’re fairly established as far as I know (well Simon Posford is anyway…)
Not had a chance to look into it too deeply and first thing I did when discover it is have a rant at The Skints for choosing a company who puts pretty much all money raised into animal vivisection (Cancer Research UK) but there do seem to be some good choices too 
Also seems you can pledge what you want to sell, from signed releases, tickets to album launch shows, actually performing gigs, t-shirts etc etc.