BluezGnome is the default Bluetooth software included with Ubuntu. It provides an notification applet which allows you to connect or send files to Bluetooth device, and a settings dialog. To connect a Bluetooth device right click on the Bluetooth icon in the notification area, and click "Preferences", than click the tab "Services", Find the service you want (such as "Input Service" for a mouse), click on it and click "Add". Sending files is a bit easier, right click the applet, and click "Send File...".
NOTE.If you don't see any Bluetooth icon like the one above, and you are using the latest version of Ubuntu, that usually means your adapter is not recognized. Refer to HardwareSupport to see which adapters work, or the Ubuntu Forums for help.