(Disclaimer: doing this may be violating the DMCA. But if you want to stick it to the man and protect your fair use rights, read on. Besides, the DCMA sucks, too.)
First, you're going to need Windows (sorry... I guess you could always use Wine or Virtualization inside Linux, but I don't have that set up yet -- I'm just dual-booting Ubuntu Edgy and Windows XP). Next, download QTFairUse which is a utility that will scrub the DRM from your music files. (There is also another utility for doing this called myFairTunes and an older one that doesn't work anymore called JHymn). Unzip the QTFairUse archive and launch the .exe file to start the program. Use the drag-and-drop interface to select which songs you want scrubbed and then click the button at the bottom to begin the conversion. You now have .m4a-format, DRM-free audio files!
Neither of these programs work under Wine... neither are in the Wine Application DB... looks like I'll have to stick with Windows (ugh) for now...
QTFairUse throws a "ImportError: MemoryLoadLibrary failed loading win32api.pyd" when using the console version and an "ImportError: MemoryLoadLibrary failed loading win32gui.pyd" when using the GUI version
myFairTunes sets up fine but throws this error when I run the application under Wine: "install the Windows version of Mono to run .NET executables" ... searched Google and it seems like this is a long way from being fixed