Wiring S

The Wiring S board is based on an ATmega644 and thus offers 32 I/O pins, 8 analog inputs, 2 hardware serial ports, 6 PWM, SPI, TWI, 3 external interrupts pins, power regulation with output for both 5V and 3.3V.

Apart from more memory, the most important extra feature is the second serial port.

The Wiring IDE offers a richer set of libraries.
An optional Play Shield acts as an adaptor for Arduino shields.

It also hosts an 24LCxx EEPROM and a RTC clock connected to the I²C bus, as well as 4 push buttons and 6 LEDs.

Learn more about the Play Shield.
Wiring, the IDE or integrated development environment, is compatible with the Wiring framework and is also platform agnostic, running on either Windows, Mac OS X or Linux. 

Looking for more features, I designed a template I could use with Xcode:  embedXcode.

Pros

  • Larger memory with 64 KB and second UART port
  • Optional adaptor for Arduino shields
  • Wiring IDE with wider and more powerful set of libraries

Cons

  • Still 8-bit based
  • User community not as vibrant as Arduino one 

Wrap-Up

  • A nice alternative to Arduino

Links

Website 
Hardware
Software
Wiki
Forum
This platform is supported by embedXcode, embedded computing on Xcode 4.