iPods support a lossless codec called Apple Lossless. It's only playable on the iPod hardware, and only encodable with the iTunes or QuickTime software, but it does allow iPods to have lossless compressed audio without installing Rockbox or other funky hacks.

I wouldn't mind seeing Apple (officially) add support to the iPod for other non-DRM codecs like Ogg Vorbis and FLAC; I don't quite understand what they would have to lose by doing so