Hackscribble CC3000 Mega Mini-Shield.
This nifty little shield connects the excellent Adafruit CC3000 WiFi Breakout to an Arduino Mega, leaving many of the Mega's digital and analogue pins unobstructed for you to use.
For an upcoming project, we needed to add WiFi to an Arduino Mega. The Adafruit CC3000 module looked ideal, and we had the choice of their shield or the smaller breakout board. Small is beautiful, so we went with the breakout.
Hard-wiring the breakout to the Mega would have been OK for our project, but we liked the idea of making something a bit more versatile. So we came up with a minimalist mini-shield that connects the breakout but doesn't get in the way of too many of the other pins on the Mega.
All but one of the pins needed by the CC3000 can be found in the Mega's double-row digital connector. Annoyingly, the IRQ pin has to connect to an Arduino interrupt pin. The nearest we found was pin 21 (SCL), which explains the lonely single header pin!
If you want to make your own mini-shield, download the Eagle CAD schematic and board layout.
Look at the README for assembly instructions and pin definitions to include in your sketch.