Ok, one of the things that I would love to do is a sort of exchange program, where people visited other worlds basically to check out and appreciate their builds, and maybe talk about their tricks while going through all the great stuff they made. Short of making something really cool like a cross-server portal mod or something (hmmm, wonder if that would be possible) maybe we just basically 'come over to your place'
Alternately we have a place to share world and frm files, then we both go to a shared server that has loaded that world, if we don't like the idea of giving out passwords. Then we could have a sort of 'world of the week' feature.
Leave a comment or a pm if you like this idea, if it goes somewhere I will put together a website for it.
Followup: I am working on a website to allow some fun stuff here.