Expose it, write your congress and state representatives, post in forums, make webpages and blogs, talk to friends and family or anyone who will listen. The man who made that movie I posted about allows people to make copys of any of his documentarys and use them for educational porposes, or just to give away for free. This website
http://reopen911.org/index.htm has a petition people can sign calling for a real independant investigation. They are also giving out free dvds to anyone who wants one that can be copied and distributed as well. There are lawsuits that can be supported by signing a petition on this site.
http://www.911forthetruth.com/
There are action alert sign ups on these sites.
http://septembereleventh.org/ http://www.911truth.org/ http://ny911truth.org/
Yet another petition can be found here.
http://justicefor911.org/
That should get you started.