GitHub has added the ability to star/unstar projects, so Gitmarks is obsolete now
Add simple project bookmarking to Github so you can "watch" projects without all their activity cluttering your dashboard. The extension uses your real browser bookmarks, so your Gitmarks will be synced nicely if you use any bookmark syncing service.
Chrome extension is here: https://chrome.google.com/webstore/detail/dbjampjhnhcfjgcapnkkbolmjghhpiio
Firefox extension is coming soon.