(Apple)Script Editor in Snow Leopard
I know I'm going to be repeating this a lot: as of Mac OS 10.6 the Script Editor application has been renamed AppleScript Editor and has been relocated from the /Applications/AppleScript/ to the /Applications/Utilities/ folder.
Also, Rosetta, which allows PowerPC-compiled applications and AppleScripts to run on Intel Macs, is an optional install. Most AppleScripts on this site are either Intel-compiled or Universal Binary, but some older scripts may not run without Rosetta (especially if you had downloaded older versions of them or those that I never got around to updating as Universal Binary). So when performing your installation of Snow Leopard it's probably a good idea to include Rosetta.