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.