While browsing the Make website the other day I came across their events calendar. We don't have many local events so I was thrilled to find a consolidated calendar that will allow me to plan ahead for a bigger trip.
You can view and add events to their calendar here: http://makezine.com/events/
One event not on their calendar that every parent should add is the yearly Free Comic Book Day. This is always the first Saturday in May and comic book stores around the country participate. Check http://www.freecomicbookday.com/ to find a participating store near you. Everyone that I've gone to has had a pile of kid friendly comics and they often have overstock items they are giving away as well.