<p>Anyone knows of a good error log beautifier? (should be able to handle apache error logs). </p>

<p>Should be open source / free, preferably with a web interface</p>

I use
http://www.librelogiciel.com/software/ScanErrLog/action_Presentation
It runs through the error log producing a summary webpage, or some other formats.  While it's best run from a regular cron-job (and it will keep a record of what it's parsed before to save effort), it can also be run as a CGI (though the demo appears to be broken).