Two programs that I personally use a lot just released upgrades:
CCleaner not only makes it really easy to empty that huge cache (and much more) but also has an excellent registry cleaner. New version 2.08.588 is now available. If this is your first time using CCleaner, during the installation, you can chose whether or not you want to install the Yahoo Toolbar (which is in the package), and whether or not you want the program to automatically check for updates. Simply a great way to occasionally 'clean-up the mess' and other unnecessary stuff on your hard drive. (For new users, exercise some caution with the advanced features!).
Fox-It Reader has significantly improved speed and compatibility with Version 2.3 (Note: The reader is free - the 'Pro Pack' is not).
Flock 1.2 reviewed previously is now out of beta. The new features can be found here.