Windows: Xdn Tweaker, which we've previously enjoyed for its fine-tuning capabilities on Windows XP and Vista, has upgraded to support the same sort of fixes and features on Windows 7, plus a few unique offerings.
As with the XP and Vista capable versions, Xdn centralises a lot of settings that are hard to get to, or just not available, through the standard Windows menus. So if you want your system to remember or not remember how you sort certain folders, edit what's accessible through the right-click menu, or de-hook Windows Media Player from all the files it tries to glom onto, Xdn does the same sorts of things for Windows 7 beta and (soon enough) RC users now, too.
Xdn Tweaker is a free download for Windows (XP, Vista, and 7) systems only. The download page recommends running the latest copies of the Windows 7 beta (and, starting tomorrow, the RC) for the best compatability, and full use of Xdn requires Administrator-level access.