I am not one to publicize a cause on my own personal sites (unless it's my own of course), but I've decided to add banners and a donate link for the National Center for Missing and Exploited Children. Check them out at the top of my blog and to the links on the right.
This is not something that I thought much about prior to having children of my own. I imagine this is the case for many people. I realize this may seem like jumping on the bandwagon, but this is definitely a cause that benefits in a positive way despite people following a fad or a trend.
There are ways people all over the country can get involved. On the web site, there are links to show how to start a program at your workplace for reporting missing children, especially if you work in a public place like a mall. Also, there is a poster program and other type programs you can get involved with. There are local offices in each state and in many cities as well - contact them and see what you can do to help.
In addition to the programs, an abundance of valuable information is there about keeping your own kids safe.