WordPress Multisite 500 Issue
Was getting 500 errors whenever attempting to access a non-existent file located within wp-content/, wp-admin/ or wp-includes/ for a multisite — in my case, this was due to an upload that no longer existed (so a fairly easy thing to trigger). Hunting around on the web lead to no useful results at the time, so
WordPress Joy #1
Ran across an issue today while re-finalizing some code for this site, and happened to break the loop on the blogroll such that it would continue listing the posts until the code timed-out.