I recommend www.myp2p.eu not only for NFL games, but pretty much any sport. I use it to watch Ohio State games online since not many are televised in the Dallas/Fort Worth metromess. Click on the "Live Sports" tab and navigate your way to the appropriate sport's page and you'll see a list of games that people are streaming. You will likely need to download a program to watch the stream. I use Stream Torrent and haven't had any issues with it not being compatible with a stream. You will sometimes find that there's only one person streaming the game you want to watch and that the image quality isn't very good. Veetle.com is a good back-up site to watch streaming sports. The selection is generally more limited but you do not need any special software or programs. It's just like watching a YouTube video. I've never seen games streamed via either of these sites get shut down. THAT seems to happen pretty frequently when I've watched stuff on justin.tv.
I hope this info has been helpful.