Some interesting forum postings:
Controlling the Push LCD with sysex, created by Adam Murray, digs out his MIDI monitor in order to track down - and conquer - placing text on the Push LCD display.
Florian Zand's Push Development Kit goes even further, providing a self-developed system for accessing the Push system. His blog page - and especially his development page - about this project can provide some interesting insight on the way the Push interacts with software.
Information in this Wiki:
The Frequency Mixer: An example of using standard Max coding to take control of the Ableton Push and create a user interface for an interesting mixing tool. There is also an 'extension' to this based on customer feedback - a master/slave combo that works across multiple channels.
PushPix: Work directly on the Push's button matrix to display a webcam video!