From my 2007 web experience definitely daloRADIUS, an open source RADIUS network management software that whoops more than 330,000 downloads to date!. One of my best achievements without a doubt. SF: https://sourceforge.net/projects/daloradius/ GH: https://github.com/lirantal/daloradius
These days one of the most fun experiences in the Node.js/MEAN stack world is leading the MEAN.JS project and releasing quite a few npm modules, one of which is apparently the first ever JavaScript library to convert CRON to Quartz format scheduler. Go figure :)