Hit the streets
Promoting free software out in the real world means getting face-to-face with real people and talking to them. There are a many different things you can do do market free software or your team or an event that you will be hosting. Always know your audience and whether they're technical or just the general public.
See also: Activism Guide
Handing out fliers and putting up posters might not be enough to get someone to go and switch on their own, but it does raise awareness about free software. The best places for flyering and postering is where people are known to be involved with technology such as computer labs in universities and colleges.
If you are doing this, you may need to ask for permission first, shops may display a poster or flyer, for a small fee. Posters outside that fall on to the street, can be classed as littering. Wet posters are again no use.
Link to hosted materials?
Try reserving a booth somewhere or getting a permit to put one up in a public center in order to show off free software. Be armed with lots of informational materials.