All platforms: Free audio editing application WavePad Sound Editor can help you cut down an MP3 to ringtone size or remix that cute voicemail. It has basic editing features such as cut, copy, paste, insert and auto-trim and effects such as amplify, normalize, envelope, sample conversion and more. WavePad has support for many audio formats including WAV, MP3, VOX, GSM, Real Audio, AU, AIF, FLAC, and OGG. WavePad also comes with voice-activated recording and a built-in CD ripper with CDDB music database lookup. For another robust sound editor, check out Audacity. WavePad is a free download for Windows, Mac, and Linux.