What are some good tools for monitoring logs on a system? I am currently using logsentry, which basically just runs grep on logs, ignores regexps I tell it to ignore, and mails me everything else, but I'd like to find something a little 'smarter', (ie can understand what a Postfix log is beyond just being a series of lines to grep on, things like that - contextual knowledge).
On services, not running anything particularly exotic - apache, memcached, postgres, postfix, openssh, squid, bind, mailman. About the strangest thing running is monotone, which I would not expect any log analyzer supports (thus, it would be nice if it is easy to extend with understanding of additional services).
Something that can parse and summarize information in hourly or daily reports (eg, 15 404s reported in this apache log file, 3 logins by this user from IPs x, y, and z, 5 mails sent by this user and 150 received by that other user, disk X is 90% full, 3000 failed ssh attempts from these random IPs, etc) would be ideal.
I've looked through several lists of log monitoring tools for Unix but most of them seem to boil down to
tail -f or
grep. I'm hoping there is something out there that I've overlooked.