Mac OS X Lion Finder's "Arrange By" Options
1. When viewing /Applications (or even [Home]/Applications), the contextual menu contains "Arrange By Application Category". This creates a System-Preferences-style view with various applications grouped according to their function. Oddly, it displays some applications as Utilities that are not in the Utilities subfolder (it shows that folder by itself).
As a developer, I was curious how these categories are formed, so I inspected Photo Booth (classified as "Entertainment") and found in its Info.list file the key "LSApplicationCategoryType" set to "public.app-category.entertainment". This seems to be how the Finder determines where to put things. Unfortunately the Finder doesn't allow items to be rearranged with the mouse, so the Info.plist seems to be the only way to fix bad categorizations.
2. There is a general "Arrange By Application" that works in any Finder window. This shows files according to what applications open them.
3. There is a new "Arrange By Date Last Opened".