This week’s TechMail is Set up rsyslog to store syslog messages in MySQL which gives a brief rundown of how to setup rsyslog to log messages in a MySQL database so that you can use a viewer such as phpLogCon in order to view/filter them. For me, this is a novelty thing more than a practical thing… grep is much more efficient and if centralized storage is what you need/want, rsyslog can do that (just like any other syslog).
But it’s a neat thing to do and could be useful for things like a server where you don’t want to give shell access but people need to be able to view logs remotely.