Till now Firefox users may be staying up-to-date with news and releases on Firefox 4 betas and nightly builds and they might have forgot about updates for Firefox 3.6.8 stable version, Firefox 3.6.9 is schedule to release on September 7 meanwhile the pre-beta for Firefox 3.6.9 released with fixes to lot of stability issues causing Firefox 3.6.8 to crash .This release is intended for testing purposes only.
As previous month Firefox 3.6.8 released, but Firefox 3.6.9 Beta (Build 1) released fixing lot of security and stability issues found in Firefox 3.6.8.
You can read Firefox 3.6.9 pre-Beta release notes , overall 65 bugs have been fixed out of which 7 are rated as critical for Windows .
Firefox 3.6.9 update to offer more stability to Firefox.
You can download this build from Mozilla FTP servers here.
Firefox 3.5.12 is also schedule to release on September 7, you can download release candidate for Firefox 3.5.12 from here.
Read Firefox 3.5.12 release candidate release notes. [source]