for visitor of my Moodle i have implemented this (very very very) sample block, named LiveHelp what uses the software LiveHelp (http://craftysyntax.com/livehelp/); this software open a windows popup what consents to converse of Moodle amministrator in real time, after installation, seems nearly a functionality interns to Moodle.
Things appear the block:
to the click appear a window popup to chat with amministrator.
This the steps:
1) Visit the site: http://craftysyntax.com/livehelp/
2) Download and install the software at: http://www.craftysyntax.com/installation.php
3) Install my block livehelp
4) configure your URL in the file livehelp_block.php... this is all.
Really simple and useful for being contacted in real time.