Hallo!
I am building a set of PHP classes to communicate with Pd. Other softs would be great too. OSC rocks, but it is UDP only.
you can also use XML-RPC to communicate with PD. Works quite well and must programming/scripting languages have implementations of the protocoll.
For PD-external see cvs: pure-data/externals/iem/iemxmlrpc
LG Georg