No one has meantioned this yet.....look for what your local area is asking for. Regions tend to use similar technology.
PHP, Python, ASP, ASP.net, JSP.....pick one for its mertits and you might find you know a great language but no one around you will hire you because they don't use it.
Pick up the paper....goto the library and look back over the last 6months to a year. Look at the jobs out there. Check the employment web sites. Get an idea of the trends and what is most sought after and go with that.