This site is your best bet for the rules of play: NFL Beginner's Guide to Football

That same site has videos of different plays and highlights too.

As far as watching games on the internet, try these:

Justin.tv - Streaming live video broadcasts for everyone

sportzpal.net - Free Live Sports on your PC, Live Football, MLB, NBA, NHL and more...

ATDHE.Net - Watch Free Live Sports TV

During the season those links get a lot of traffic depending on the teams. Sometimes the feeds work great and sometimes not so much.

Hope that helped. Glad you like American football. I love it!