If you can hear it, you can record it - Record any application's audio, including VoIP calls from Skype, web streams from Safari, and much more. Save audio from hardware devices like microphones and mixers as well. You can even record all the audio heard on your Mac at once! If you can hear it, Audio Hijack can record it.

Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere.

Marked allows you to preview your Markdown (in any flavor) as you write in your favorite text editor. It tracks your file changes and updates the preview as you go, even automatically scrolling to the point in the file where you're currently working.