TIOBE: The monthly programming languages index

An interesting link to analyse the trends and maybe plan your future is the TIOBE Programming Community Index.
This is a monthly updated chart of programming languages highlighting those that are moving up and other moving down.
The criteria being considered are defined in the TIOBE site.
Also interesting is the "Long Term trands" section, showing data since 2001 and the very long term.
All of these are sections in the link above (you'll have to scroll down).