Always free operating system for desktops, servers and netbooks. All the flavour with only half the fat. Currently in beta, the new version of Ubuntu will be released on Thursday 28th April, just in time for the holidays.
The Ubuntu developers are moving quickly to bring you the absolute latest and greatest software the open source community has to offer. Ubuntu 11.04 "Natty Narwhal" Beta 2 gives a preview of the next version of Ubuntu.
Upgrade from Ubuntu 10.10
To upgrade from Ubuntu 10.10 on a desktop system, press Alt+F2, type in "update-manager -d" (without the quotes), and press Enter. Update Manager will open up and display the message, "New distribution release '11.04' is available." Click Upgrade and follow the on-screen instructions.
To upgrade from Ubuntu 10.10 on a server system, install the package update-manager-core if it is not already installed. Then execute the command sudo do-release-upgrade -d, and follow the on-screen instructions. Note that the server upgrade is now more robust, and thus will utilize GNU screen and automatically re-attach in case unexpected problems arise, e.g. dropped connection problems.
The same instructions apply to all other editions of Ubuntu (such as Kubuntu, Xubuntu, etc.)
You can also download for Windows to run from a USB stick without interfering with Windows on your PC. Also available for Macs as a replacement for OSX