ODAI (Open Distributed Applications Interface)
ODAI is a simple library to provide you with similar mechanism like XMLRPC or CORBA but claims to be smaller, faster and much easier to use. As there is no IDL compiler involved or any information about the other process needs to be known at compile time except a port number or socket path, everything is done at runtime by the library.
Support for int, double and char * as function and return parameter, asynchronous delivery of errors via callback registration, very simple API, exported functions are declared exactly the same as normal c functions, return values are passed as call by reference variables directly to the remote function call.
There is some kind of problem on sending a server message (bonus feature) under very high load, as sometimes a process just hangs.