Under Windows I 've used a block of named shared memory to pass data between applications.  You use CreateFileMapping() and MapViewOfFile() on one side and OpenFileMapping() and MapViewOfFile() on the other.  However you need to be very careful about unsynchronized access into the memory from multiple applications and must use the heavy weight named synchronization objects which are quite expensive.

In my case it work very well in a pipelined system where events were triggered in one app when data was available for consumption in other apps.

Peter