Evernote is the best note taking app due to its availability across most platforms and its powerful features. You can go to their website, use their mobile apps, or get hardcore and download their software. You should check out the program even if you're not accustomed to taking notes, it might just improve your productivity.
FreeRice is a way of building your vocabulary while doing a good deed. The website is sponsored by the World Food Programme which aims to help end world hunger. On FreeRice, you are presented with vocabulary questions. For every vocabulary question you get right, the World Food Programme will donate 10 grains of rice to help fight world hunger. Pretty cool, right? FreeRice also has options for answering questions about geography, foreign languages, paintings, and more.
Grooveshark lets you search for songs and play them. You can find just about any song as a high quality mp3. Other sites charge for what Grooveshark offers for free.