Intrusion Detection Systems

I need some tools to monitor an ip network for intrusion detection.
Can someone help me with this ?
I tried before some public domain tools like argus but i need to know is
someone has successfully constrcuted a good & complete intrusion detection
solution (i.e monitoring, logging, real-time alarms, proactive monitoring,

I'm also interested in the developement of such a solutions, and i may
coordinate the distributed developement effort with coordination with
academic projects focusing the same goal.

Best regards