Thumboo is a free thumbnail generator that lets you create screenshots of any website instantly. You can then download the thumbnail in multiple sizes (150×100, 200×150, 300×250, and fullxfull). They also have an API you can utilize for your own web apps.
Awesome find! I’ve been making a fair few website thumbnails lately and it always takes a few minutes via Photoshop to get them just right. I’ll definitely be using this service frequently!