Learn a new programming language

Recently I came across Ohloh, the open source network. And got me thinking again how many programming languages do I really know.

This short list pretty much sums it up:

• C#/.NET
• T-SQL
• Javascript

And then some HTML, XAML and CSS.

I see myself more of a voyager of the programming seas, having looked upon the lands of:
C/C++, Java, Delphi, Ruby, Python, Haskell, CLisp, Groovy, Dart, PHP, F#, Visual Basic, NASM, Perl

I also came across Seven Languages in Seven Weeks: A Pragmatic Guide to Learning Programming Languages doing some googling.

Personally I think learning seven programming languages in seven weeks is generally a bad idea.
My lex parsimoniae test is this:
You are proficient with a programming language if and only if you can generate a continuous profit from your efforts.

I have read many articles and discussions regarding which programming languages to learn.
In general, it's a good idea to know at least one of each:

• Domain Specific Language (ex. HTML/CSS)
• Functional Language (ex. Haskell, F#)
• Strongly Typed Language (ex. C#, Java)
• Object-oriented Language (ex. Delphi, PHP, C#)
• Dynamic Language (ex. Groovy, Ruby, Python)

In general I believe it's not how many you know, but rather, how many you can use. All of us learned our first programming language by placing our focus solely upon it.

With the same effort we applied to the first, we should apply to the next.

I believe it's much better to improve on what you know than to be a jack-of-all-trades in languages you will never use.