I use DropBox (free) to keep my Scripts folders in sync across two Macs. It works great. You move the ~/Library/Scripts folder to the DropBox folder, then make a symbolic link (not an alias) of the moved Scripts folder, and then you move the symbolic link back to where you moved the original Scripts folder from.

You can use an alias but the results aren't as good. Some programs won't be able to access the scripts through the alias (OmniFocus is one). The symbolic link solves that problem.

I used Automator to make the symbolic link in 10.5. I think, but I'm not sure, that there is a command in the 10.6 Finder's File menu to make a symbolic link, and that would be even easier.

One weird thing: DropBox seems to update/sync every time a script is run, as if the script has somehow changed during the run. Doesn't seem to affect anything but the Growl notifications are a surprise.