I've never actually had to set up one of these systems before but I had researched it and found the following vendors:

Commercial SEM products include EventTracker by Prism Microsystems, RSA enVision, TriGeo, Q1Labs QRadar, ArcSight, SenSage, Cisco Security MARS, Snare and others.

Open Source SEM products include OSSIM, and Prelude.

Personaly, I think the tools given with the OS is sufficient enough if you create the correct security audits and logs. But, I guess that depends on your network infrastructure.

Envision and ArcSite are the best.

You can use an open tool like Snare if you wish.

You will need to understand what you want to capture and configure the devices accordingly.

I believe ArcSite and Envision have out of the box reporting.