I recently presented at OpenDNS's S4 event where I spoke about using Bro. Linked below are the slides I presented and the lab material I created for this event. I encourage people to work through the labs to gain experience programming Bro and getting an understand for what all it can do.
OVA (with Bro installed and all labs ready to be worked on)
OVA MD5 (for ensuring you're OVA download is correct)