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: 
My opinion is that it is just like any other development environment. Do you standardize on one development language? Why? The same should be true for your scripting environment. Not only do I lean toward standardizing on a specific language I think you should standardize all the same things that you are hopefully doing in your programming environment (naming conventions, coding style, etc). Of course there are counter arguments and there will occasionally be exceptions, but hopefully they would be few and for valid reasons.
Per Project, anything checked in should probably follow a rule of minimal complexity.

Your team will be gone some day, and someone else will have to come in and maintain this. Please don't make them learn 5 languages or they are going to look for your names in the source code an hunt you down.

When we've picked up hack projects like that, we've pretty much considered the creators complete fools and made fun of them. They couldn't bother themselves to learn one scripting language???

That said, if you don't check it in--who cares?