Canonical has just released the latest version of Ubuntu, 11.10 Oneiric Ocelot, to end users. Most prominent among its new features are upgrades to the Unity interface, the new shell introduced in version 11.04. New users can download the open source OS from the Ubuntu web site, and current users can try their luck upgrading their existing install through the Update Manager.
Other changes include the replacement of the Evolution email client with Mozilla Thunderbird, version 3.0 of the Linux kernel, and the ability for developers to sell software through the Ubuntu Software Center. Newer versions of Ubuntu's built-in apps, including Firefox and OpenOffice, are also included.
Ubuntu is officially available in both 32-bit and 64-bit versions, though ports (and forks like Kubuntu and Xubuntu) are available for other architectures and platforms as well. The next release, 12.04 ("Precise Pangolin"), is due in April of 2012, and will be an "LTS" or Long Term Support version supported by Canonical for three years after its release.