Post an event
Regional events
Most chapter pages list regional events on their left sidebar, for example http://publiclab.org/wiki/gulf-coast. Look in the sidebar for the "post an event" button to add yours. If you have recently created a new region page and wish to add event listings & a "post an event" button to your sidebar, tag your page with events:theregionname, for example events:gulf-coast. If you have questions, email web@publiclab.org.
Google calendar
We also have a Google calendar, which is how you get listed on the http://publiclab.org/events page. To have your event shown on this calendar, email organizers@publiclab.org.
How to host an event
Want some advice on hosting an event -- how to reach people, what to provide, how long it should be, etc? Take a look at the Host a Balloon Mapping Workshop page for some great tips.