[TYPO3] htaccess rewrite for multiple installations on one core

[Luc Franken]

Hello Typo3 and server guru's,

I have a question regarding installing multiple installations on one 
shared hosting account. I have already running one installation with 30+ 
domains. The performance is not very great so I want to seperate the 
biggest sites into seperate installs with symlinks etcetera.

I managed to get the installation working. So now I have something like:

http://domain.com/site1/index.php
http://domain.com/site2/index.php

These sites use the same core and it works great. Now I want to get them 
working nicely bij calling them like:

http://site1.com/
http://site2.com/

And that is the problem. How can I write an htaccess file which 
understands that it should rewrite everything from domain site1 to 
subfolder site1?

Also links to good documentation is really appreaciated!

Thanks in advance for your time!

Best Regards,

Luc Franken
TenToday development