Freeware

I consider this a program for advanced users. Be careful with it.
Download & Info

BleachBit quickly frees disk space and tirelessly guards your privacy. Free cache, delete cookies, clear Internet history, shred temporary files, delete logs, and discard junk you didn’t know was there. Designed for Linux and Windows systems, it wipes clean 90 applications including Firefox, Internet Explorer, Adobe Flash, Google Chrome, Opera, Safari,and more. Beyond simply deleting files, BleachBit includes advanced features such as shredding files to prevent recovery, wiping free disk space to hide traces of files deleted by other applications, and vacuuming Firefox to make it faster. Better than free, BleachBit is open source.
Multi-platform: Linux and Windows
BleachBit 0.8.3 cleans more Opera, WinRAR, Adobe Reader, Windows logs; improves wiping speed; adds menu options; add a Lithuanian translation; and updates other 18 translations.

[Read more…] about BleachBit 0.8.3 Released

Mozilla has released Firefox 3.6.13 & Thunderbird 3.1.7. Download them from the previous links or update from within the program (Help / Check for Updates).

Firefox 3.6.13 fixes the following issues found in previous versions of Firefox 3.6:
* Fixed several security issues.
* Fixed several stability issues.

Thunderbird 3.1.7 fixes the following issues in Thunderbird 3.1.6:
* Several fixes to improve performance, stability and security, see the Security Advisory.
* Several fixes to improve handling of large folder files stored locally.
* Several fixes to improve corruption in local copy of IMAP mailboxes.

Download (source)

Autoruns v10.06: This release fixes a bug that could affect delete and disable operations on entries stored as multisz registry values.

What is Autoruns?

This utility, which has the most comprehensive knowledge of auto-starting locations of any startup monitor, shows you what programs are configured to run during system bootup or login, and shows you the entries in the order Windows processes them. These programs include ones in your startup folder, Run, RunOnce, and other Registry keys. You can configure Autoruns to show other locations, including Explorer shell extensions, toolbars, browser helper objects, Winlogon notifications, auto-start services, and much more. Autoruns goes way beyond the MSConfig utility bundled with Windows Me and XP.

Download CCleaner (slim)
Is this version a little slow on startup for anyone else?

Change log:
* Improved application startup time and INI loading speeds.
* Removed need to reboot for Index.dat cleaning.
* Improved cookie cleaning in Firefox 4.0 Beta 7.
* Improved Chromium based browser detection and cleaning.
* Added support for Adobe Reader 10 and Acronis True Image.
* Improved cleaning for 7-Zip, Adobe Reader 9.0, Microsoft Silverlight Isolated Storage, WinPatrol and Microsoft Management Console.
* Added support for local domains in “Cookies to Keep” list.
* Improved debugging with log file support using /DEBUG command-line parameter.
* Improved detection algorithm for 64-bit and Program Files.
* Improved folder drag and drop in Include options.
* Fixed bug in Uninstall Tool during cancellation.
* Improved drive detection in Drive Wiper screen.
* Added support to refresh cleaning rules using F5.
* Improved translations.
* Minor GUI improvements.

Microsoft/Sysinternals updates: Process Explorer v14.01, Autoruns v10.05 (source Sysinternals Blog)

Process Explorer v14.01: This update fixes a bug related to the DLL view and adds a tab to the new system information dialog, Summary, that displays all the performance graphs together.

Autoruns v10.05: This Autoruns update adds ActiveSync autostart locations, fixes a bug in that prevented offline scanning from working in some cases, and fixes a formatting bug in the scheduled tasks display.

This a a new version of CCleaner. Download CCleaner. According to the forums there is no longer a “slim” version.
*edit – apparently the forums were mistaken, The slim version showed up.

* A new 64-bit native EXE designed specifically for 64-bit systems.
* A new Drive Wiper tool screen under the Tools section, which allows users to securely erase the contents or free space on a specified drive.
* Improved support for Internet Explorer 9 and the Google Chrome browsers.
* We have also added improved cleaning support for HTML5 database storage, allowing CCleaner to effectively manage the next generation of web applications.
* Additional cleaning support for Microsoft Silverlight Isolated Storage.
* We’ve added three new environment variables (%SystemDirectory%, %SystemDirectory32%, and %SystemDirectory64%).
* New application icon.
* New Intelligent cookie keeping feature.
* and more…

Download or update from within the program (Help / Check for Updates).

Thunderbird 3.1.6 fixes the following issues in Thunderbird 3.1.5:
* Fixes a critical security issue that could potentially allow remote code execution. This issue does not affect email or newsgroups but could be triggered through browser-like features or add-ons.

Download or update from within the program (Help / Check for Updates).

What’s New in Firefox 3.6.12
Firefox 3.6.12 fixes a critical security issue that could potentially allow remote code execution.

*note – As of this writing Thunderbird 3.1.6 is currently being pushed to mirrors but is not out yet.