The Ubuntu 13.10 Saucy Salamander final beta announcement went out this morning though download links have been available since last night. All flavors of Ubuntu are available in 13.10 Beta versions including Ubuntu Server, Ubuntu Core, and the Ubuntu Cloud images. Ubuntu Touch / Ubuntu for Phones is also available in a testing state.
More details on the beta release can be found via the mailing list announcement, which also provides links to the other derivative announcements like Edubuntu and Xubuntu.
For more details on the Ubuntu 13.10 features and performance changes see our many Ubuntu 13.10 articles. More Ubuntu 13.10 benchmarks are forthcoming.