robonobo is social music sharing and downloading software. It allows you to share your friends' music libraries and playlists, stream the audio instantly, and download the file in the background so you can burn it, export it to your music player, or do whatever you want with it. You can import your friends list and share links to your playlists via Facebook and Twitter.
The TI-BASIC Compiler allows you to write TI-BASIC programs for the Texas Instruments TI-83 and TI-84+ calculators using your computer instead of the calculator's keyboard. This allows you to spend more time writing code than navigating menus or trying to scroll around the tiny screen on the calculator.