We've had polls on audio players, so as an extension of that - What audio file format do you use/prefer? And why? My preferences have changed over time ... I've gone from MP3 to MP4/AAC back to MP3 and my preferred format is now Ogg Vorbis. I've tried most formats including Monkey aka APE, FLAC, WAV, WMA ... While the lossless formats are great for an audiophile, storage isn't infinite (on a PC or portable device) or practical. The other consideration is available support in portable or other audio devices. Portable players are starting to support file formats from the ogg project aka Ogg, FLAC, Speex; but commonly the majority support the three mainstream formats, MP3, MP4/AAC, WMA. I have settled on Ogg Vorbis for a few reasons ... "fully open, non-proprietary, patent-and-royalty-free" and all in all it has great compression and delivers outstanding quality. It should be reasonable to assume the most popular choice will likely be MP3 followed distantly by WMA and AAC/MP4 (Apple's standard) ... I'm curious to see how popular they are and also see if any of the less mainstream file formats are popular.