Most any audio player worth their salt will natively support FLAC. FLAC is pretty uncommon for consumers because it is a lossless format, which means all of the original data is retained so it has a bunch of data that you likely will not be able to perceive, and consequently the file sizes are about 3-4 times what a comparable MP3 file will be. Audiophiles and even trained professionals will be hard pressed to hear the different between a properly encoded 320kbps MP3, Vorbis (OGG), and FLAC files, but FLAC does have its place, in the professional side. Personally, my favorite place for FLAC files is from Bandcamp. You can also rip tracks from audio CDs and save them as FLACs as well. Just bear in mind that FLAC files will only sound as good as the source - there isn't anything else inherently superior about FLAC other than it retains 100% of the source data. Personally, I recommend Vorbis, but I don't think iDevices support it well - it is natively supported on Linux, Android, and most players in Windows. VLC is an excellent crossplatform player that will play both FLAC and Vorbis (.ogg).