Does anybody know of any good CPU mineable coins?

I'd like to take advantage of the idle CPU power on my Mac Pro Xeons and I figure that there must be some CPU mineable coins by design.

CPU mineable coins are an interesting idea; they are CPU mineable because

A) they are non-paralellizable and
B) the use too much memory for a GPU

Bitcoin as a currency is a 'waste', because it's Proof of Work is trivial and (ultimately) useless. It is a difficult problem that currently, from what I've last heard, each transaction uses enough energy to power a home for a week. That's a lot of cycles being used to solve this problem, but the sheer number of people and value of it builds that type of network for that type of currency.