and plenty more. The Propeller is commonly used because it's high performance, has easy video output, and offers a lot of I/O.
So What is the Propeller Platform?
The Propeller Platform puts the Prop on a circuit board with voltage regulators, memory, a crystal, and connectors to other modules. It's a lot like the Arduino with a few improvements on the basic idea;
1 - Modules (a.k.a. shields) can be connected to each other on top and bottom. For example, you might have a Propeller module in the middle, an LCD UI on the top, and a prototyper on the bottom.
2 - Pin spacing is .1". The space between sockets is .2", too. This makes the Platform compatible with breadboards, and it lets you use Platform modules in combination with other project boards.
3 - The board footprint is 3.8" x 2.5", which is the same footprint as ExpressPCB's MiniBoard service, so adding your own custom module is inexpensive and straightforward.
4 - They're well documented. They're featured in Jon Williams' column in Nuts and Volts and the Propeller Platform Module will be the basis for many of projects described in his upcoming columns.
5 - They're Public Domain. Module designs use the MIT license, giving you more flexibility than more restrictive licenses like Creative Commons Share-Alike. Templates and specifications can be downloaded here.
The Propeller Platform is available as a kit or pre-assembled from Gadget Gangster.
Build time is about 45 minutes. Get started by going to the next step!
The Propeller Platform is an open-source embedded computing platform - it's a lot like the Arduino, but improves on the concept by using a faster microcontroller, standard pin spacing and a less restrictive license (MIT License).
What are the specs?
Built-in video generator hardware to output to NTSC/PAL or VGA displays
Built-in high level language (Spin) that's easy to learn
High performance (160 Million Operations per Second)
Speed can be changed at run-time for improved power efficiency
Available in a hobbyist-friendly DIP package
32 I/O pins, each pin can be set as an input or output
The Propeller Platform adds:
5v and 3.3v Voltage Regulators, rated at 800mA, each
5Mhz Crystal, user-swappable
32kB on-board memory, with space for a second memory IC
All IC's are in sockets for easier replacement and assembly
Standard .1" pin headers in a dual-row configuration, so modules can be stacked above and below or added to a breadboard or Protoboard
More Expensive The Arduino is $30, a Propeller Platform with PropPlug (what you use to program the Prop) is $50. But you'll only need one PropPlug and a Propeller Platform on it's own is $35.
Smaller Community You'll see the word 'Arduino' in Make Magazine a lot more often than the word 'Propeller'.
No onboard 'Analog In' Instead, you have to use a capacitor and a resistor to read analog values. Not hard, but not as easy as the Arduino.
2 Chips You need 2 IC's when using a Propeller, the Prop itself, and the EEPROM to store the program
Much faster microcontroller WAAY Faster. This lets you do really cool things like output VGA, do speech synthesis, play .wav files, and more, all on the chip. The Propeller does 160 MIPS while an atmega168 does 16.
Hi-quality audio and video The hardware for video is builtin and numerous audio libraries are available under the MIT license.
Real Multitasking tell one cog to take care of video and another to handle the keyboard / mouse, and that's it. No interrupts, no timers - it's REALLY easy to do multitasking on the Propeller
More I/O, More Flexible Each I/O can be reconfigured, and there are 32 of them.
Standard Pin Spacing The Propeller Platform fits on a breadboard or protoboard
Better Power Usage The Prop can change clockspeeds on-the-fly to save power and shutdown un-used cogs. Power usage can go from 80mA all the way down to 4-5mA
Better License Arduino is licensed under Creative Commons Attribution Share-alike (read it - it's several pages). The Propeller Platform is available under the MIT license (read it - it's 2 paragraphs). Don't worry about how you use our designs - we won't sue!
Software focused A lot of microcontrollers have dedicated hardware to accomplish certain tasks. Instead, the Propeller does most stuff in software. This doesn't bother me, but some people have problems with it.
Spin The high-level language for the Prop is Spin - this is a much more modern language than C/C++, but it takes a little getting used to
Mac Support There is no official Mac client, but getting up and running with a Mac isn't hard. Parallax has a Mac page right here.
Personally, I use the Propeller for most development, and I use a PICaxe (read: 08M the 555 of our time?) when I just need simple / cheap logic. The Arduino is 'aight, but I find the Propeller easier to program and a lot more powerful. The Arduino is too expensive when I just need simple logic.
What modules are available?
There is no definitive list of modules, but you can check Gadget Gangster for some of the modules currently available. Some example modules: