A fairly basic sprite packer.
Supports square output only, with optional power-of-2 dimensions and grid-based layout. Outputs spritesheet description as JSON.
Browser support is somewhat limited but it should work in relatively modern versions of Chrome, Firefox, and IE.
I mostly just wanted to see how hard it would be to use the HTML5 File API to do some simple image processing. Turns out it's not that hard!
Made for #toolboxjam.