javadoc like commenting..
i'm surprised that nobody mentioned javadoc (http://java.sun.com/j2se/1.3/docs/tooldocs/solaris/javadoc.html) like commenting. Javadoc makes making documentation a whole lot easier.
You just have to include
* This is a doc comment.
* @see java.lang.Object
all those after the @ sign are headers for the documentation for that specific functions. There are other utilities for C as well that can autogenerate documentation like this. BTW this was mentioned in an article relating to documentation, here in Freshmeat. Worth mentioning in an article on commenting.
/* large code piece here */
could be used for commenting out large code pieces which does have comments inside making commenting out a headache.
dont' forget the Cache Now (http://electraglide.geog.unsw.edu.au/CacheNow/) project.. they'v got some interesting ideas as well..