JSTorrent is a bittorent application for Google Chrome OS and it works on Intel and ARM based Chromebooks. Here is the official description:
The new and improved JSTorrent is a BitTorrent client for Chrome that downloads torrent files with ease. It can download torrents directly to your Downloads folder and can handle large files (multi-gigabyte files) with ease. It also runs fine on lower end ARM Chromebooks.
The App is regularly updated and has a large user base. One of the qualities that I look for in every Chrome app and extension. That being said, the app is still getting polished, and you might find bugs here and there, especially on ARM Chromebooks.