With the collection page of hidden features of various languages and
frameworks, I think it would make a great session at a monthly meeting
to go over some or all of these features. Some are really very clever,
and immediately useful.

The overall collection of links is here:

http://beerpla.net/2009/06/21/hidden-features-of-perl-php-javascript-c-c-c-java-ruby-python-and-others-collection-of-incredibly-useful-lists/

and the individual lists of hidden features, sorted by popularity:

Ruby

http://stackoverflow.com/questions/63998/hidden-features-of-ruby

Ruby on Rails

http://stackoverflow.com/questions/709679/hidden-features-of-ruby-on-rails

Javascript

http://stackoverflow.com/questions/61088/hidden-features-of-javascript

Also of interest might be the database tricks, CSS, jQuery, etc.

Best regards,

Lester