The Ubuntu team has now released the second beta version of Ubuntu 11.10, also known as Oneiric Ocelot. This is the last development release before the final version, which is scheduled for October 13th. Changes since beta 1 include kernel and Gnome updates, inclusion of OneConf for synchronizing software installations between computers, and improved support of 32-bit software on 64-bit systems.
Oneiric Ocelot, meaning something like "dreamy cat", which will wake you up with a refurbished Unity desktop interface and a revised Ubuntu Software Centre with thousands of free applications and new "top rated" views.
You can download the latest beta version from various mirror sites. Keep in mind that beta releases are not suitable for mission critical systems.
For more information see Oneiric's technical overview.