You didn't mention the price range to which you wanted to confine yourself. Any of the Macs will be up to the task. Until you let us know the price range, I'll mention the three hundred dollar Zoom H4 which will provide you with a handy digital recorder with built-in microphones, jacks for better microphones in the future and a USB interface for connection to the Mac.
http://www.samsontech.com/products/p...fm?prodID=1901
Garageband is a good way to start out. It is free and will allow you to make multi-track recordings. Once you've mastered it, you may find you want additional capabilities or you may find that it is all you need.