3 monitoring programs in one????

Well not really.  This article does a good job of explaining the difference between Nagios, Icinga and Opsview.  At the core these are all Nagios though.  Missing from this set is Groundwork Opensource which is also based on Nagios, which we reviewed last year.  If you haven't looked at the original or these two alternatives give the article a look.  If you are evaluating Network Monitoring/Datacenter Monitoring solutions to check out Zenoss, we we also reviewed last year.  While inspired by Nagios it is a completely new process.  But as a testiment to how awesome Nagios is still can use any Nagios plugins that you just can't live without.

Do you do centralized logging?

One of the things that can really save you or your Admin's time is a centralized logging server.  I came across this article about how to set one up on either GenToo or Ubuntu.  It's a great how to that would get you started.  If you are looking for something really powerful I would suggest looking at Splunk.  Splunk is a  great tool to help you group, filter and analyze your logs.  There are very few other solutions.  If you have a solution for managing your logs please post it in the comments.  If I can get more than just Splunk I will try to do a more in-depth review of the options everyone suggests.