Westi and I are into the new core plugin, Health Check. We're seeking additional test ideas.
The current set of tests are the following:
http://plugins.trac.wordpress.org/browser/health-check/branches/alpha/hc-tests/php-configuration.php
I've a few database tests planned, and Peter has a few more on his todo list:
http://plugins.trac.wordpress.org/browser/health-check/branches/alpha/hc-tests/writing-tests.txt
If you've a grudge against additional php parameters, or if you're aware of topics that are related to server niggles and that could qualify as test worthy, please speak out.
PS: someone please make this thread sticky for a couple of days.