Cycling '74 and Ableton have introduce Max For Live - a visual programming toolkit that adds an "edit button" to Live.
Though Max For Live is just out, beta testers have already been giving it a workout. Here are some examples that demonstrate the types of doors that Max For Live opens up for Live users:
Buffer Shuffler, above, is a "premium" audio effect that comes as part of Max For Live.
Here's a demo of m4l.lab.serialin - an Arduino controller for Max For Live. A 4-control sensor is mapped to MIDI control messages that can be routed inside Live for events or modulation.
SevenUpLive 2.0 is a complete port of SevenUpLive to MAX For Live.
7up Live is a Java application that combines 8 different monome applications into one interface. With it, your monome or monome-style device can communicate with Ableton Live via MIDI.
Stretta demos using polygome with a monome and Max For Live.
Check out the links below for more resources for getting started with Max For Live.
If you've got other suggestions, or a cool Max For Live example, leave a comment below.
Mr Kyteman gives a performance and a rundown of the modular rig he used for performance at Modulation