Welcome to the forums, Marko. From an PM I sent earlier:
There are only a few languages worth learning these days for webappsec. .NET (if you want to do Microsoft programming), Java, PHP, and Ruby on Rails. Everything else is sort of dying unless you are talking about low level languages. All of those languages are doing better than ever. So it depends on what sorts of languages you are interested in (fast dev/prototyping or slow dev/enterprise production software).
I focused on the prototyping languages primarily (PERL, PHP, etc...) because they are quicker to test applications with, although I often have to delve into the other languages during penetration tests. Having a good working knowledge of all of them can't hurt.
- RSnake
Gotta love it.
http://ha.ckers.org