You would probably be better using a Proxy (e.g. Squid) , for your internet access, and something like Sarg to analyse the logs.
You might like to look at Ipcop, Advanced Proxy and Sarg if you are looking for an open source Firewall/Proxy/Logging Analysis solution.
(Start here
http://www.ipcop.org/ and here
http://sarg.sourceforge.net/ )
The reason I suggest this, is because logging and analysing the browser history is a huge task in itself, and probably far removed from the idea behind Open Audit.