Question: At work we write a small to moderate amount of scripts to aid us in normal development. We have some people that are more comfortable in python, some in perl, some in php, etc...

Sometimes I think it is best to let people work in a language they are most comfortable with. This can mean that sometimes people can do a better job on a script (as they know more tricks in one language). It can also lead to less development time per script.

Other times I think that we would benefit the most from standardizing so that there might be more shared libraries and so that we don't get into the situation of "I can't work on that script because I don't know python".

Do you think that we should standardize or let people choose for each script they write?

Answer: 
I would advocate standardizing on a couple languages. "Thou shalt use either Python, or Perl, or Ruby. Not Rexx, nor PHP, nor NewBatch, nor aught other, for thy brethren ought to be able to read thine writing without undue despair or cutting of their skins".
So long as the languages in question are used for scripting, I agree with other commenters that it should be left to the devteam, and different languages should be tolerated in most cases.

If the language is used for your main codebase, you had better standardize on one.

If some developers complain about a script not written in their language, encourage them to learn it, particularly if it's one of the widespread ones like Ruby, Perl, et al.