Do you know of a company that will buy unused cpu cycles?

So I came across bitcoin and I did a bit of research.  From what I understand is that bitcoins are backed on nothing but the time used for the cpus to create them. 

When creating bitcoins what exactly are our CPU's processing?  Are we using this processing power like seti@home or foldinghome types of programs?

Lets say a man gets a job digging ditches, he digs 1 ditch an hour and makes $10 USD an hour.  This mans work is turned into a hole in the ground.

When bitcoins program is running it uses cpu power and makes X bitcoins an hour.   What is the CPUs equivalent to a hole in the ground?


Also it seems like since I didn't get into creating bitcoins from the very start it's just not worth my electric bill to create more bitcoins. 



Are there companies that will buy extra CPU or GPU cycles? 

It seems like since these bitcoins are now a functioning working currency backed by time, that a working business model would be to sell processing power based on what people are willing to pay for it in USD, EUR, gold or even bitcoins.