Below is a script I worked up so that I could easily resize photos for my photography section. It uses the Big Cat Script Plugin by Ranchero Software. (Also home to NetNewsWire)

There are a few things to note about the script. First, it edits the file you choose, so make sure it's a copy. Second, the script will prompt you for what size you want to resize to and then do it's thing. Once it's done it will display a dialog stating that it's done.

Enjoy!

--Open this script in a new Script Editor window.

on main(filelist)
    
    set theSize to choose from list {"100", "150", "200", "480", "640"} with prompt "What size do you want to scale to?"
    
    repeat with i from 1 to (count of filelist)
        set this_file to (item i of filelist) as string
        
        tell application "Image Events"
            activate
            set this_image to open file this_file as alias
            scale this_image to size theSize as integer
            save this_image --with icon
            close this_image
        end tell
        
    end repeat
    
    display dialog "Resize completed."
    
end main