Syslog Analyser Tool

Hi

Could anyone recommend a good, preferably free Syslog Analyser Tool I can use with my Astaro SG200 (running V9) to analyse the web filter logs in more detail.

I'm trying to get a feel for volumes of web traffic per user, over time, the in built reporting is great as far as it goes but it doesn't let me analyse uaage at our peak times within a single day.

Thanks in advance for your help and advice. :)

Steve