Ubuntu 8.10 beta is out, if you can wait for the final release then download the 8.10 beta now!

I’ll be updating mine. If you already have Ubuntu installed and you want to upgrade from Ubuntu 8.04, press Alt+F2 and type in “update-manager -d”. Update Manager should open up and tell you: New distribution release ‘8.10′ is available. Click Upgrade and follow the on-screen instructions.