The DTE RS-232 module is a tight and tidy way to convert RS-232 (computer-level) signals down to a microcontroller level signal strengths. DCE means it's configured as a "Data Communications Equipment" (with 9 holes).
The Solarbotics Arduino Freeduino Enclosure (SAFE) is a laser-cut acrylic case for your Arduino Mega. It also has the added feature that it can house an Arduino or Freeduino instead with a MEGA amount of space left inside.
Love the Netduino but not a big fan of pulling out the ol' soldering iron when it comes to prototyping with it? The Netduino Go Starter Kit gives users the ability to interface Godbus modules to the Go for quick and easy plug-and-play projects.