As I continue to explore the world of Arduino, I started looking for cheap Arduinos to use in projects – permanent projects that need a dedicated microcontroller. Once you’ve got an Arduino and start having fun with it, you think about things you can build, but you always want one around for prototyping and trying out new ideas, so for permanent installation, you’ll want a cheap Arduino you can drop in place.
Now, since Arudino is open source hardware anyone could get the parts themselves and assemble and use/sell an “Arduino-based” board. This is great, and it’s why I love open source, and it provides many choices. That said, if you are not the “build your own from scratch” kind of person, keep reading for some kits that may work for you.
These are the cheap Arduinos I found, with some notes on each. All of them require some sort of of FTDI connector, as they do not have USB connections. This is fine for boards that will find their way into projects that do not need to be connected directly to a computer, the idea being, you buy one FTDI connector, and you can use it to program all of these boards. Each vendor should also have an FTDI connector for sale, for instance, SparkFun’s FTDI Basic Breakout 5V, Adafruit’s USB FTDI TTL-232 cable, etc. (You will need to figure out the whole 5V or 3.3V thing.) Also worth mentioning is that most of these are kits, which means you’ll need to be comfortable soldering small pieces to make them functional. (Shipping costs you see below are typically estimates, with the choice of the lowest cost.)

Photo from Solarbotics
Ardweeny probably wins the prize for smallest Arduino, as the “board” and the components actually sit on top of the chip! It’s a novel idea, that’s for sure. If you want a super-cheap Arduino to plug into a breadboard, this is it.
Pros: Cheap – under $10, Very small
Cons: You can’t replace the chip*, so if it gets blown, you’re out of luck, No easy way to power it, Requires FTDI to program it
Now, if you want to “free your Ardweeny from the breadboard” you can get an Ardweeny BackPack which provides power, and a few other niceties. It’s $11.95, which makes teaming it with an Ardweeny total more than $20, which doesn’t make a ton of sense to me… It’s a neat idea, but it all seems a little weird.
Maker Shed has it for $9.95 + $6.95 shipping and Solarbotics has it for $9.95 + $6.94 shipping but note that Solarbotics has a $5.00 “handling fee” if you place an order under $30.

Photo from The Makerspace
PicoDuino is another small Arduino. I don’t know much about “The Makerspace” and their web site doesn’t really provide much info on them. I do like their description of the product “We designed the Picoduino to be small, cheap, and disposable so that you can throw it in a project and forget about it.”
Pros: Cheap – just $10, Small, The chip is in a socket, so it is replaceable
Cons: No easy way to power it, Don’t know much about “The Makerspace”
Similar to how the Ardweeny has it’s backpack, the PicoDuino has it’s PicoDuino Shield Adapter, which makes using it in a more traditional fashion a little bit easier. The adapter is $10, same price as the PicoDuino itself.
The Makerspace has it for $10.00 + $5.00 shipping.

Photo from Modern Device
Really Bare Bones Board (or RBBB) is a step-up in the small/cheap Arduino world. It’s got an easy to connect power jack, a socket for the chip, and the board itself is a bit “customizable” as far as the size you want it to be.
Pros: Affordable – under $13, Power jack, Customizable board size, Chip is socketed
Cons: Still need an FTDI connection (maybe)
I really like the specs of the RBBB. Also note, you can buy one fully assembled for $22.00 if that’s more your style.
Modern Device has it for $12.95 + $4.00 shipping, and The Shoppe at Wulfden has it for $12.00 + $2.00 shipping.

Photo by ladyada – Some Rights Reserved
BoArduino comes from Adafruit Industries, and looks to be pretty similar to the RBBB with perhaps just a few more niceties and features.
Pros: Affordable – $17.50, ICSP header, “No-Wait” bootloader, “protection” diode
Cons: A bit more expensive than the other options
Adafruit has it for $17.50 + $3.99 shipping. (Occasionally Adafruit offers 10% discounts on kits, so if you’re lucky you could get it for $15.75, which would just get you in under the $20 barrier including shipping.)
(Note that Adafruit also has a USB version of the BoArduino, which swaps the DC power jack for a mini-USB connection and comes in at $25.00)

Photo from SparkFun Electronics
Arduino Pro Mini comes from SparkFun Electronics and it’s damn small. In fact, it’s miniature! It’s also not really a kit, as it comes assembled (you just need to add header pins.) The chip is surface mounted, so it’s non-replaceable. Again, size is the #1 feature of the Pro Mini.
Pros: Affordable – $18.95, Small, Really Small
Cons: More expensive than the other options, non-replaceable* chip
SparkFun Electronics has it for $18.95 + $4.41 shipping. (That’s the 3.3V version. There is also a 5V version.)
(Note that SparkFun also has the Arduino Pro which is just a dollar more, and comes in 3.3V and 5V versions as well, but at almost $20 and a surface mounted chip, I’m not as interested in this one.)

Photo by Windell H. Oskay, www.evilmadscientist.com – Some Rights Reserved
Diavolino comes from Evil Mad Science, and it’s red, and has flames. The Diavolino does not come with a socket for the chip, so add another $1.50 or so if you want one. As for power, you can get a battery pack for an extra $1.00. There’s an extremely detailed assembly guide which I think any beginner would be comfortable following.
Pros: Cheap – $13.00, Nice power options
Cons: Large, No socket included
Evil Mad Science has it for $13.00 + $5.55 shipping.
So that’s my quick rundown of cheap (non-USB) Arduino boards. It should be noted that almost all of these get cheaper as you buy more of them. For instance, the RBBB is $12.50 for one, but just $9.50 each when you buy 10 of them. Also, while it makes the most sense to use an FTDI cable to program these, for any of the boards that use a socketed chip, you should be able to pull the chip, put it in a USB-equipped Arduino, program it, and then return it to the non-USB board. In theory anyway… Note that I also didn’t really talk about what model these are based on, most appear to be based on the Duemilanove or the slightly older Diecimila. How you use it will determine if this matters much. All boards mentioned use the ATmega328, though many show outdated photos with older chips on their product pages, so always read the specs!
And if this isn’t enough, take a look at the spreadsheet of many more Arduinos, which may be slightly dated, but is definitely a nice long list.
(Update: When I say something is “not replaceable” it may be better to say “not easily replaceable” at least by a beginner. — Thanks to Milwaukee Makerspace for pointing this out.)