Waterloo Region is bustling with tech events and meetups, many of which involve Free and Open Source Software communities. One excellent listing of these events is the WatCamp calendar. KWLUG members Bob Jonkman and Chris Craig are heavily involved in curating this calendar of events. (The current version of the WatCamp site is kind of broken, so it might be better to visit the HTML version).
Following the WatCamp calendar (via iCal, RSS or something else) is the best way to keep on top of local tech events. However, KWLUG maintains a partial list of relevant groups, including a list of nearby Linux User Groups, and several groups in Waterloo Region which are attended by other KWLUG members.