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!
http://mathias-kettner.de/checkmk_writing_checks.html

Using Dell OpenManage with Check_MK
http://flakrat.blogspot.com/2011/03/using-checkopenmanage-with-checkmk.html

OMD Installation and Check_MK Configuration at ORCA / Breakable Experimental Network
https://geni-orca.renci.org/trac/wiki/OMDconfiguration

From the same site: Using Eventhandlers for automatic Inventory & deletion of KVM VMshttps://geni-orca.renci.org/trac/wiki/OMDeventhandlers

Using Check_MK to monitor the "DTC" hosting control panel
http://dtcsupport.gplhost.com/PmWiki/Nagios

Ignoring services based on advanced syntax with explanations:
http://deranfangvomende.wordpress.com/2011/08/31/check_mk-magic-dust-for-ignoring-stuff/

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

http://sysadmin-101.blogspot.de/search/label/checkmk