Oh, and don't fall for the "so other people can read your code" trick. Trust me, NOBODY wants to read your code! Unless, of course, they are trying to re-write it in their favorite language.
I don't think this is necessarily the case. If I'm using your code to do something scientifically interesting, then I most definitely DO want to read it. If your code crashes on my data, then I'm going to read it to figure out why (and probably fire up the debugger if necessary).
And even if I don't read your code, the fact that I have the ability to makes me more likely to try it out (in my experience, there's a general trend relating software I can't read with software that has irritating bugs).
That said, I'm probably in the minority of "other people". And I'm probably not going to read the boring parts of a program unless I suspect there's a problem with them.
For my two cents on the original question - if you're using a library, use the language that library's written in. Otherwise, use whatever language you feel most comfortable expressing the solution to your problem in.
Pete
