Divshot works great as a prototyping tool for Rails projects (and if you're using something like Angular for templating, you can do much much more with it). We

Divshot works great as a prototyping tool for Rails projects (and if you're using something like Angular for templating, you can do much much more with it). We built http://revision.io/ http://revision.io/ for the Rails Rumble last year (2nd place, woo!) and used Divshot to prototype all of the interfaces. It's a huge time-saver, but I'm a bit biased :)