Grow more plants and help clean up the air!
Another thing you could do is leave your car at home and take the bus.

A new Yahoo group has been formed for people who use Capital Metro busses in
Austin Texas called http://groups.yahoo.com/group/busridersaustin/

It is meant for discussion, meeting and advocacy of issues important to
Austinites who rely on public transit.

I did search around before I started it but didn't find anything like this
group.