As you may know: to run AppleScripts that were compiled on a PowerPC machine on Intel machines (and therefore Snow Leopard) requires Rosettaan optional install on your SL install disc. While Rosetta is a fairly small install, some people have expressed an interest in staying Rosetta-free. There are quite a few of these types of AppleScripts here on the site and I'm working on updating them to Universal Binary (although a good percentage of these in the Retro Scripts category probably won't be updated by virtue of being obsolete). Long-time visitors may also have some of these scripts in their collections.
While you could wait for me to update these kinds of scripts to UBdisclosure: one of these days I will get around to admitting that I am a notorious procrastinatoryou can update these scripts yourself by doing what I would do: open the script in AppleScript Editor, noting whether it is a compiled Script (.scpt) or an Application (.app), and re-save it. It will be re-compiled for your machine type, and if it is an Intel machine, will run without Rosetta. The "Run Only" and "Startup Screen" checkboxes can be left unchecked. Script Applications that use idle handlers need to be checked "Stay Open".
During the Save, if AppleScript Editor informs you that the "Document Format is Read Only: This script application is in a format that is no longer supported...", the case for non-bundled applications compiled pre-SL, just click the "Save As" button, and proceed with the save. In Snow Leopard, single-file-type apps are no longer supported. The defacto Application type is a bundle.
The AppleScript Release Note: 10.6 Changes page at Apple has more on this.