Ubuntu 10.04 which is based on Debian distribution available today on their website. The version is LTS version which mean it is a long term support for the OS. It includes three years of support through free security and maintenance updates.

New in 10.04 LTS:

• Boot speed: Noticeably quicker on almost any machine and super-fast on SSD-based machines such as netbooks, which means users can speed straight to the browser for fast web access.
• Social from the start: The new ‘Me Menu’ in Ubuntu 10.04 LTS consolidates the process of accessing and updating social networks including Facebook, Digg, Twitter and Identi.ca. The Me Menu also integrates chat channels so users can talk with friends or colleagues on Google Talk, MSN, IRC and nearly every network.
• Ubuntu One: Enhanced desktop integration for the online service means files and folders can be shared and saved on the cloud more easily. Bookmark and contacts sharing has been added, speeding the move from personal computer to personal computing.
• Ubuntu One Music Store: Music from the world’s largest labels and greatest bands available direct to Ubuntu users through the default music player. Purchase tracks, store in Ubuntu One and share DRM-free music from one location across multiple computers and devices.
• Ubuntu Software Centre 2.0: An easy way to find new software, and keep track of it once it’s installed in a new, sleeker interface. Users can also single out software provided by Ubuntu, by Canonical partners or by developers who use Canonical’s Launchpad Personal Package Archive (PPA) hosting service.
• Ubuntu 10.04 Netbook Edition (UNE): As well as benefiting from the improvements in the Desktop Edition, netbook users will see even faster boot speeds on SSD-based devices, faster suspend/resume that will extend battery life –  and the industry-leading interface for these smaller screens.