
Hot Corners, is one of my favourite navigation features. If you're like me, you tend to have a lot of windows and applications open at once. In your System Preferences pane, go to Expose and Spaces, and pick Active Screen Corners, I like my top right corner to tile all open windows and my lower right corner to clear all windows and expose the Desktop.
You can add a photo or logo to your email signature by opening up the signature dialogue in your mail program and simply dragging the image directly onto that particular signature from either the finder or the iPhoto application.

Need to translate text or full webpages, use the Google translator at http://translate.google.com/ . This free tool will allow you to translate over 50 languages
iTunes Radio contains access to hundreds of radio stations worldwide in every genre.

To type fractions go into the keyboard language drop down menu near the top right of your screen (the flag beside the clock) and choose to "show character viewer". From there you choose symbols, then number and number symbols, pick the fraction you want and click insert.