I'll admit the first things that came to mind were "in" jokes and wnff meme type things but a serious one isn't a bad idea.
I was thinking along the lines of a wiki that could be used to record the early years of the Nats while we still remember them, and then of course continue into the present. The other day I Googled up a question about the original sale to the Lerners and couldn't find the info I wanted, but I did find some great quotes from Stan Kasten, it would be good to store all of that stuff in one spot where it would be easy to find five, ten, and twenty years from now.
This is something that a small group like WNFF could get started but would require a much larger group to fill in the hundreds or thousands of possible pages. It would be cool to get the final analysis of controversial decisions such as Bowden's failure to trade Soriano documented, but there would also have to be tons of shorter write-ups for guys like Rob Mackowiak. The old Senators and Greys information would be a nice too.
Certainly a WNFF page with the in jokes would have to be included, but that sort of stuff would not drive the page views or enough general interest to make such an undertaking sustainable. It would have to be more along the lines of
http://awoiaf.westeros.org/, a comprehensive go-to source for the Nats team history.