Multiskilled programmers are very much preferred. Don't be afraid to specialise where you wish, but any programmer worth their salt won't invest their future in a handful of technologies and will usually try to learn a few languages to complement their industry. Personally I have learned PHP, Python and Ruby (all useful in web development!) - I'm out of practice in Java but I could brush that up very quickly if needed. You'll quickly find learning multiple languages is not that difficult - they all have various syntax differences but the overall theme and language structure are often quite common. Java and PHP5 even look similar...
Even in a specific segment like PHP, you'll also need familiarity with a few database types. MySQL is a given, but MSSQL is also popular.
Other skills worth having include Linux/Unix and BSD knowledge (all are similar, and Linux is a doddle to get started with), shell scripting for Linux, and really just the basics of compiling the interpreters/environments for your chosen languages, how to configure them, and very importantly - security practices for each.
As you can guess from that list, it's best to start with just one language/technology and specialise there. Over time work on the others - I try to learn the basics of at least one language every year or two (enough to create a simple application). Also keep an eye on the application frameworks (e.g. Ruby's Rails, PHP's Zend Framework/Symfony/phpCake) for each and specialise in at least one (assuming they offer more than one