Audacity - Free, open source, cross-platform audio software.
FFMPEG - A complete, cross-platform solution to record, convert and stream audio and video.
MP3 Recorder - Record all what you hear.
Sound Editor - Free Sound Editor.
Channel Vocoder - Creative voice transformation at your fingertips!
Stereo Mix - this blog can help you to solve "Stereo Mix" issues
BPM Calculator - nice freeware program can detect BPM values of MP3 and WAV files.