jQuery plugin for client side torrent file creation using HTML5 FileAPI
Yes, it's terribly slow compared to native torrent generator applications, but hey, we're in the browser world!

Works with browsers listed at:
http://caniuse.com/#search=blobbuilder

Thanks:
Dmitry Dedukhin (https://github.com/dmitry-dedukhin) for Blob.slice fixing code
Chris Veness (http://www.movable-type.co.uk/scripts/sha1.html) for sha1 implementation
Andrej A Antonov (https://github.com/polymorphm) for various javascript tips
Alexis Deveria (http://a.deveria.com/) for that awesome When Can I Use site