Audio Companion
Rip CDs, convert .mp3 to .wav, and record audio from a sound card.

MAD
MPEG Audio Decoder implemented with 100% fixed-point operations, ideal for systems without a floating point unit; distributed under GPL. Source available for download.

MP3 to Wave Converter
Simple and easy-to-use Windows application for batch converting MP3s to WAV files; by Acoustica. Limited demo version available for download.

Xaudio
Free multiplatform MP3 Playback Toolkit and decoding libraries for all platforms and CPUs. Especially targeted at MPEG Audio (MP1, MP2 and MP3) decoding.

MP3 Convert It!
One click conversion of .mp3 to .wav. Drag and drop supported.

Audio CD Maker
Create audio CDs from .mp3 with drag and drop feature. Decoder function included.

MP3 Decoder Review
List of mp3 decoders and links to the accuracy of the decoding engines.

MP3 WAV Converter
Decodes MP3 files into WAV format for burning onto a CD. Features an intuitive interface, batch conversions, and normalization. Demo version available for download.