#Thumblerific#
Thumblerific lets you make thumbnails from image urls. It runs on Google App Engine.
It works like this
Say you find a hosted image
http://somesite.com/image.jpg
with thumblerific you could make a 90px thumbnail for that image like this
http://thumblerific.appsppot.com/t?image_url=http://somesite.com/image.jpg&width=90
This also allows you to make thumbnails on the fly from your html, calling the <img> tag.
Its that easy and simple.
You can check a demo here
##INSTALL##
Use Google App Engine