lightningtimer.net
A simple (but extremely useful) timer for lightning talks. Now powered by Github pages.
Usage
Visit http://henare.github.com/lightningtimer.net/ and click Start to begin.
The default time is 5 minutes but you can customise this by adding '#SECONDS' to the URL, e.g.
Contribute
Pull requests accepted.
Credits
Written by @simonw, put on Github pages by @henare when he discovered http://lightningtimer.net/ wasn't responding.