Mozilla has released Firefox 3.5 Beta 4 (formerly known as Firefox 3.1) and is available in over 70 languages.
This beta includes a faster TraceMonkey JavaScript engine, enhancements to private browsing, and location aware browsing.
For a full list of changes you can read the release notes.
Existing beta users should have the upload pushed out to them, and new testers can download the latest beta from Mozilla.