Of which PHP is pretty much the case study of that; it was originally a bag of tricks used by one guy, who put it online, then other people started using it, expanding it... and the rest is history. At least that's my understanding of it. Don't know enough about other languages actually to think of other cases; most common languages were at least designed a little bit, AFAIK (e.g. Java was made to be portable, and reasonable enough to work in).
Or the counterexamples, which, I guess isn't so much "counter", as a generalization? Some of those early languages designed by committee (Ada? FORTRAN? I forget which was the most notorious) could just as well be subjective with respect to to the committee as a whole.
Tim