I learned a lot of programming languages over the years, from arcane stuff like IBM 390 assembler and PIC microprocessor assembler to PL/1, COBOL, PROLOG to languages that are actually usefull like C, C++, Java, C# or Python. At the moment I use mostly C# under Windows and Python as a scripting languages on both Windows and Linux. There is a whole range of languages that I would like to take a deeper look at but my other hobbies take up too much time nowadays, so Ruby, Haskell, Smalltalk and Lisp will not get the attention I'd like to give them (at least not in the near future).
I still hope for more unconventional languages on the .NET / mono plattform, like the F# attempts to implement a ML based language or the IronPython attempt. In the meantime, C# has to suffice.