The folks at SketchUp have just released a new maintenance release of SketchUp 8 today. It contains some bug fixes including one that appeared when Apple pushed an update for Safari. But the main thing you'll notice is a change in the icons. the one for sketchUp will look like this:
Most likely when you open SketchUp you'll be prompted to get the update. If you don't you can go to SketchUp.com and download it.