how about nicehash? this site lets you purchase mining power based on contracts.  you've got to choose what algorithm you want and the duration on which the miner would run.  i understand there are buyers and sellers of hashpowers in the site.  and the site just connects the sellers and the buyers, and i assume it gets some cut.  recently there was a big theft that left a big mark on their reputation.  but the company is surviving now and i think everything goes well as of now.