For starters, welcome to community credit. I did receive your email earlier today, but am happy that you posted the question on the discussion board so that others in similar situations can benefit.
To answer your question regarding contributions in the past, yes they can definitely be submitted. Many people tend to do that to have a complete online profile. In your case, as will others, you have a number of contributions from other sources and you are wondering about automating the process. I will be happy to work with you on that, let's take it on a case by case basis. DotNetSlackers, for example, we will be integrating community credit into their forums (and possibly other areas ) in the very near future. I can chat with Sonu about that. He and I have recently been discussing implementing the Community Server add-on into his forums. We are just waiting on the release of the 2007 version. For things like CodeCamps, it will probably be easier to just submit them manually.
Overall, it should all be possible via a combination of automated and manual submissions, but hopefully alot more automated than manual.