This is a modification of the schematic for the RS232 serial loader to show how to hook a MAX232 to an Arduino. It is not a shield - just a little kludge board that can be added to any microcontroller. You can put the MAX232 on several of the available shields, some of which have small breadboarding areas.
A minimal Arduino MAX232 circuit consists of a the device and four capacitors. It can be connected to the serial port in several ways, though. Shown are a MAX232 connected as a DCE and a DTE, using RTS/CTS handshake. The RS232 pinouts shown are for the 9-pin DB9 standard connector.
You can also use the Arduino MAX232 as a +/-10V power supply, as seen in the schematic below.
Here is an interesting use of a MAX232 as an ultrasonic transmitter.