We are encouraging everyone to share raw files as FLAC files, to save bandwidth and server space.
Encoding files can save huge amounts of space and time, and the conversion utilities listed below make converting to WAV or AIF very quick and painless. Some DAWs support FLAC natively, too, though you might find they use more resources than with WAV.
If you have already posted multitrack files, you can leave them as WAV, or convert them to FLAC. If you convert them, please link to this post, where people unfamiliar with FLAC can learn about it.
You can find some good FLAC conversion utilities on Google, as well as here:
APE encoder/decoder for Windows:http://www.monkeysaudio.com/download.html
APE/FLAC/... encoder/decoder for Mac:https://www.macupdate.com/app/mac/14246/xact
FLAC command line tools for Windows:http://sourceforge.net/projects/flac/files/flac-win/
GUI for FLAC command line tools for Windows:http://flacfrontend.sf.net/
Converter and CD ripper for Windows with FLAC support:http://www.freac.org/
Great Audio Editor with FLAC support for Linux, Windows and Mac:http://audacity.sourceforge.net/
Switch, a multi-format converter for both Windows and Mac, which is not free though ($30 currently):http://www.nch.com.au/switch/index.html
(Thanks to Stoman for putting this list together!)