Firewall log analyzer suggestion

I have several client sites using Netgear firewalls, mostly the FVS318. When the log space on each firewall fills up, the contents are e-mailed to me and Mail rules place them in an appropriate folder. I'd like to be able to analyze the logs I've collected in much the same way Apache log files can be analyzed with Webalizer or AWstats. Can anyone suggest software to do this? Free is good, but non-free utilities will also be considered.