there are couple of them but you have make sure your router is compatible with them, DD-WRT, Tomato, open-wrt. I personally use DD-WRT and it works great.
Originally Posted by GH0
Follow these instructions: http://dd-wrt.com/wiki/index.php/Ver...er_Information
Since we can't link to all the tools correctly now, follow those instructions and do what it says exactly. If you screw it up, then you may end up bricking your router.