I use Imageready droplets. (They need Photoshop/Imageready.)
http://share.studio.adobe.com/axBrow...ctType.asp?t=6
I only use this for its watermarking ability but it also does image resizing and stuff.
http://www.scriptsoftware.com/iwatermark/
Even iPhoto will export images at set sizes and compression but that is probably not what you are looking for.