PewPew 1.2 should be accepted anytime now, so the scores are going to start to pour in... luckily I have just completed PewPew's website:
The most important features are the score board and the forum. I made the score board myself in python, and found the code for the forum here. The forum is pretty cool, because it allows you to post with your Google account, or without login at all.
Everything is hosted on the Google App Engine, so if the traffic stays under a limit, I will never have to pay for the servers, and the website will stay up and running for ever.
According to my estimations, I can handle 100 000 score submissions per day without paying for additional bandwidth. Since "only" 50 000 people have installed PewPew, I should be fine.
I have no idea what to expect regarding the CPU utilization, but I have cached a lot of database calls, so I should be OK.
At worse, I might have to pay 1 or 2$ per day during the first week; after the first week, the traffic should decrease significantly.