http://harvestcoin.com/ is another pool where you don't need to register.
well, mining unregistered is nice and easy, every noob can do it. So if you have writen some software you can ask people to mine for you for a short time if they like your software. This is getting you more in return than asking for a small donation of real money. Another good thing is that you don't have to go to the pool site to see how much coins you have mined and if it's over the limit for checkout. The pool is sending your mined coins automaticaly to your wallet.