During the month of May I went to AusCERT and Confidence to talk about OSSEC (i.e. Log analysis using OSSEC). On both presentations I mentioned LIDS (Log-Based intrusion detection), and provided an overview of the ossec architecture and how to write decoders and rules. If you want to learn a bit more about ossec, take a look at them.
**Note that both presentations are very similar, but the AusCERT one is a bit more organized, so recommended to be read first.
Hope you enjoy!