These are hand-picked howtos that explain something about running Nagios+Check_MK with enough bonus info to let the reader understand no just the 4 lines of config for solving a single Check_MK config issue, but also the inner workings that turn 200 lines of Nagios config into 4 lines of Check_MK config.

My site also has a lot of Check_MK howtos that should enable you to run a more fine-tuned setup.

You should not miss the official documentation!

Using Dell OpenManage with Check_MK

OMD Installation and Check_MK Configuration at ORCA / Breakable Experimental Network

From the same site: Using Eventhandlers for automatic Inventory & deletion of KVM VMs

Using Check_MK to monitor the "DTC" hosting control panel

Ignoring services based on advanced syntax with explanations:

Chris Carmichael's notes and howtos. Always fun to read notes from really skilled Windows admins!