Script for community (community)?

With age, our student get-together gathers less and less.
Communication is becoming more and more virtual.
This is an objective process.
In order not to be limited to letters and messages via ICQ
we did chat, forum, etc.
But the most optimal we see a closed community
Tipo communities in LJ or a little easier than Habra.

Stupidly to open a community in LiveJournal is an inappropriate option
Since many at work address www.livejournal.com
blocked by admins.

There is a normal hosting where you could put some script.
')
So the question is:
Can anyone recommend a php + mysql script to make it look like the LJ community?