I would suggest Ubuntu 9.10, but if it runs really slow on your notebook, try Ubuntu 9.04 - you wont be disappointed.
We are running CentOS 5.4 at work, so it is cool to play with the latest and greatest Linux distro at home. SUSE and Fedora also comes highly recommended for Linux newbies.
And now that Google Chrome 4 is in beta and available for Ubuntu, I just cant be happier.