I am a big fan of syslog-ng, and personally used it to handle 5 million syslog messages per day with mysql on a single server.
However this syslog server (rsyslog) seems interesting, and here is a comparison between the 2 syslog servers:
It has all the nice features of syslog-ng in addition to other features like:
- Support backup back-end database
- Support more databases like MS-SQL, sybase
- Native support for sending emails
- Native support to send SNMP traps
You can also use a web front-end with it http://www.phplogcon.org/ , also http://code.google.com/p/php-syslog-ng/ can be used.