Play .wma, Ogg, and FLAC Files in ITunes - PC World
http://www.pcworld.com/article/169606/play_wma_ogg_and_flac_files_in_itunes.html?tk=rss_news

Audiophiles love FLAC files for their lossless fidelity, while Ogg and WMA files aren't widely supported. With free plug-ins, all three of those formats can be played and managed in iTunes.