QuickTime 7.6.6 for Leopard is recommended for all QuickTime 7 users and according to Apple brings about "general reliability improvements for iMovie." Additionally, the update addresses a long list of security vulnerabilities related to maliciously crafted audio or movie files that could allow attackers to cause crashes or run arbitrary code. The update is available via Software Update or the Apple Support Downloads page. (Free, 68.63 MB)
Set Per-Folder Views in the Finder
Tired of navigating to a particular folder and having to switch to List View every time? With Finder in Leopard, you can set viewing preference for each individual folder. Just navigate to it, and set the view the way you want (Column, List, Icon, or Cover Flow). Then choose View > Show View Options (Command-J) and in the window that appears, select the Always Open In... checkbox.