They are all tied together.
Learn one and you become capable in all of them.
You will also begin to feel the demand to learn something about all of them.
Regarding demand and relevance.
Learn ASP.NET (Visual Studio 2005) which is actually a framework.
The language itself is a combination of languages.
The easy answer is Visual Basic - or c#......
Many people will disagree but the fact is visual basic is the Microsoft Animal and they own the commercial server market.
Also being proficient in ASP.net means you can develop applications for both the desktop and the internet.
There are no other languages which offer this versatility and the market dominance AND such a beginner friendly SDK as visual studio. (That last statement means the learning curve aint so bad). The biggest drawback to learning this language is that it contributes to success of MICRO$OFT which many folks dont like. Be that as it may the demand is uber high and their compiler is the bomb diggity.
And to repeat - learn one language, you will basically "get" them all. It's all just, if - than - else - for - variables - arrays - strings - integers - objects - methods - properties.
Learn those 11 things and you can wax on w/ any programmer in any language.