Streamers automates the process of recording streams, using Ambrosia Software's WireTap
, and converting them to .m4a or .mp3 in iTunes. You can build a list of streams to record immediately or to schedule for later recording. The program also lets you maintain a library of shows that can be recorded on a weekly, monthly, or daily basis. (Streamers uses iCal for scheduling.) The source is included, and others are encourage to tinker - and especially to try their hands at adding .wma and QuickTime support.
As a practical matter, I use this to maintain the latest of various NPR shows on my ipod. Some of these are included in the Library by default.