The languages you would expect are installed on Jones, like C, C++, Java, Ruby, Perl and Python, plus probably Objective C somewhere. Besides that, Prolog, Chez Scheme and OCaml are available.
There are some things you should know, however.
- Java is at 1.5 because it's Apple's custom distribution, which lags behind Sun's official one.
Python 2.5 is installed, but available as python2.5; Python 2.3 remains as python so that the system can continue to use it for maintenance.
- OCaml is pretty fast (the same as C++, more or less) but not especially easy on memory. Its syntax is the worst Pascal dregs that you can imagine, and its semantics is that of Scheme.
- Chez Scheme is also supposed to be pretty fast. I would expect it to have similar performance characteristics to OCaml. But you don't have to wrestle with a typed compiler or terrible syntax. On the other hand, the OCaml library is a lot bigger.
- PHP is not installed, that I know of.