I can get them all working together but it's a wiring mess. I'd like a simple I2C hub (like an Arduino Sensor shield) that I can plug them all into. I reconfigure things a lot and plugging in five connectors is a lot easier (and less prone to error) than trying to connect up 20 individual wires. The I2C items are:
LCD shield, Compass , color sensor, MP3 board. I can put JST RE connectors on all of them, which is my favorite connector because it's compact and easy to make your own custom cables but I need a simple board to plug them into. I have a bunch of analog and digital sensors and I just plug them into a Mega I/O sensor shield.
I'm playing around with a robot that has 1 distance sensor, 5 proximity sensors (left, right, rear, front down, rear down), 3 servos, 2 drive motors, a sound sensor, a motion detector, a temperature sensor, a gps, an SD card, 2 motor encoders plus the I2C: LCD shield, Compass , color sensor, MP3 board. I'm also potentially adding XBEE, an RFID reader and an arm. It's already a mess of cables and without IO shields and 3 or 4 pin connectors it gets really ugly. It's enough just getting all the separate libraries for that stuff to behave with each other.