I am a Treasurer for a 501c3 organization. What are the rules for holding bingo, gambling as fund raisers for charatible purposes?

The reguations depend on your particular state. In CA, for example, you have to register the event, and you're limited to the types of games you can play (no slot machines, for example). See: Bureau of Gambling Control - Charitable Gambling Registration Program - California Dept. of Justice - Office of the Attorney General (http://ag.ca.gov/gambling/charitable.php) Do a Google search combining your state name and "charitable gaming" and you should be directed to a site with the specific regulations for your state.