Synthesia is a very cool game for beginner, novice and expert piano players. At first sight it looks a little bit like Guitar Hero, but now it is used for piano. Here are some more screenshots. Nice about synthesia is that it is free. The free version can load all the midi files you want, but does not show any sheet music. If you want to see the sheet music you have to buy Synthesia for $18.
I have a Wacom tablet which a very nice pointing device when drawing vector images, but did you know you could paint with it as well? MyPaint and ArtRage are both great tools to paint virtually. Unfortunately MyPaint is not available for the OSX platform. Interested? Check out the examples made in MyPaint and ArtRage.
AppCleaner is a free tool which helps you to remove an application completely from your harddisk. If you remove an application in OSX you simply drag it to the thrash. The application is then removed, but some small garbage might be left. AppCleaner makes sure everything is cleaned. The nice thing: it is free!
Bonjour (mDNS) via OpenVPN on Linux with Avahi-deamon
A customer of mine asked if there was an equivalent of Photo booth to use on Windows. On the web I found Snap! a user friendly tool which can apply some funny tricks on your webcam image including mirror, text-balloons and more.