Since my forum is running well and it's a part of another website, we want to show the last 5 threads, polls, new members etc. on that website.
I'm stuck with it, don't know exactly what to include and what it has to get out of the database.

Thanks in advance!

This shouldn't be a hard problem? You have 2 options:
1. Use vbulletin functions include alot etc.
2. Do this:
Connect to the database from vbulletin.
Mod the top5 query's to the standard php query format,
and mod the template's to echo"html" etc. or the template system you're using.
Shouldn't be a hard job!