I have all of my CDs ripped in FLAC. As mentioned above, FLAC is a free open source lossless codec. This means no DRM, and you're not tied to a proprietary format like AAC and ALAC. I stream it wirelessly to a Squeezebox connected to my receiver - sounds perfect.

There is a free FLAC codec enabling you to play FLAC files with most players - Windows Media Player, WinAmp and foobar2000 being examples. The Squeezebox/Slimserver interface handles them natively as well.

For iPod use, etc, I used foobar2000 to convert the FLAC files to mp3s at fairly low bitrates. Therefore I have 2 copies of each track - one lossless FLAC copy for critical listening and one mp3 at 96k for portable media player use. Given how relatively cheap hard drives are these days, this isn't that big of a deal.