user4970: I have been thinking of a million things to do with my Arduino, but those things are extremely simple and it would leave my Arduino as a $25 waste. 
For example, programming Arduino to control my living room lights with my smartphone ... I was thinking of connecting the Arduino in the wall, onto the light switch wires. I am looking for a "permanent" solution, but I figure this would leave me with a $25 waste of circuitry inside my wall.
Are there any "Arduino" types of electronics that perhaps have many less ports, JUST enough to get a single task done?

user710: There are good instructions here:
http://arduino.cc/en/Main/Standalone
and here:
http://arduino.cc/en/Tutorial/ArduinoToBreadboard
Alternatively you can go for an Arduino mini http://arduino.cc/en/Main/ArduinoBoardMini or a corresponding Chinese clone.

user27: This is a typical scenario for an Arduino Uno board: you buy one and use it for prototyping your project. Once done, you design your own PCB, as small as possible, connecting only the required wires to the ATMega328p.
For the next project, you buy another ATMega328p (just the MCU), plug it on the Uno and start again.

user4971: I've had the same exact problem.
Since I like developing using the Arduino IDE I've created an how to assemble a board using just Thru Hole Components to replace the Official board.
Please visit the following link for further information http://jpralves.net/cseduino
All the components will cost about 5 USD.

user3031: You can embed a bootloaded ATMega328 (or any of the other compatible ATMega processors) http://arduino.cc/en/pmwiki.php?n=Main/Standalone in your project. That way, you will only need the processor and a couple of components, setting you back only a couple of dollars and saving quite a lot of space:
http://arduino.cc/en/pmwiki.php?n=Main/Standalone
If that is one bridge to far, you can have a look at the Arduino Pro or Arduino Pro Mini. Those boards are complete boards, only smaller and cheaper, and specifically designed for a more definitive use in projects.
If you need even more space and cost reduction, you can switch to a stand-alone ATTiny processor. The better models of those can also contain an Arduino program. Instructables has this great tutorial that shows you how to use an ATTiny85 or ATTiny45 as a lightweight 'Arduino'. 
Recently, I have tried to use an ATTiny13A for a project, but that one only has 1KB of flash memory, which leaves you with hardly any space for the Arduino bootloader, let alone your program, so therefor I chose to program it directly using AVR Studio, at which point I think you cannot in any way call it an Arduino project anymore. :) Still, it's not that different. You only miss out on some of the library functions, and the implied application loop.

user4969: Digispark comes to mind, or any of the ATTiny breakout boards at Tindie. Or, make your own PCBs, I just now finished soldering a few ATMega328p circuits to boards I designed. Microcontroller is $1.50, PCBs range from $2 to $8 each, time is "free."
Also consider "compatible with" designs; while you're not directly supporting the ecosystem, if you've already paid full price once and your conscience is clear, eBay has plenty.

4970: <p>I have been thinking of a million things to do with my Arduino, but those things are extremely simple and it would leave my Arduino as a $25 waste. </p>

<p>For example, programming Arduino to control my living room lights with my smartphone ... I was thinking of connecting the Arduino in the wall, onto the light switch wires. I am looking for a "permanent" solution, but I figure this would leave me with a $25 waste of circuitry inside my wall.</p>

<p>Are there any "Arduino" types of electronics that perhaps have many less ports, JUST enough to get a single task done?</p>
 710: <p>There are good instructions here:</p>

<p><a href="http://arduino.cc/en/Main/Standalone" rel="nofollow">http://arduino.cc/en/Main/Standalone</a></p>

<p>and here:</p>

<p><a href="http://arduino.cc/en/Tutorial/ArduinoToBreadboard" rel="nofollow">http://arduino.cc/en/Tutorial/ArduinoToBreadboard</a></p>

<p>Alternatively you can go for an <em>Arduino mini</em> <a href="http://arduino.cc/en/Main/ArduinoBoardMini" rel="nofollow">http://arduino.cc/en/Main/ArduinoBoardMini</a> or a corresponding Chinese clone.</p>
 27: <p>This is a typical scenario for an <a href="http://store.arduino.cc/index.php?main_page=product_info&amp;products_code=A000066" rel="nofollow">Arduino Uno</a> board: you buy one and use it for prototyping your project. Once done, you design your own PCB, as small as possible, connecting only the required wires to the ATMega328p.</p>

<p>For the next project, you buy another ATMega328p (just the MCU), plug it on the Uno and start again.</p>
 4971: <p>I've had the same exact problem.</p>

<p>Since I like developing using the Arduino IDE I've created an how to assemble a board using just Thru Hole Components to replace the Official board.</p>

<p>Please visit the following link for further information <a href="http://jpralves.net/cseduino" rel="nofollow">http://jpralves.net/cseduino</a>
All the components will cost about 5 USD.</p>
 3031: <p>You can embed a bootloaded ATMega328 (or any of the other compatible ATMega processors) <a href="http://arduino.cc/en/pmwiki.php?n=Main/Standalone" rel="nofollow noreferrer">http://arduino.cc/en/pmwiki.php?n=Main/Standalone</a> in your project. That way, you will only need the processor and a couple of components, setting you back only a couple of dollars <em>and</em> saving quite a lot of space:</p>

<p><a href="http://arduino.cc/en/pmwiki.php?n=Main/Standalone" rel="nofollow noreferrer">http://arduino.cc/en/pmwiki.php?n=Main/Standalone</a></p>

<p>If that is one bridge to far, you can have a look at the Arduino Pro or <a href="http://arduino.cc/en/Main/ArduinoBoardProMini" rel="nofollow noreferrer">Arduino Pro Mini</a>. Those boards are complete boards, only smaller and cheaper, and specifically designed for a more definitive use in projects.</p>

<p>If you need even more space and cost reduction, you can switch to a stand-alone ATTiny processor. The better models of those can also contain an Arduino program. <em>Instructables</em> has this <a href="http://www.instructables.com/id/Program-an-ATtiny-with-Arduino/" rel="nofollow noreferrer">great tutorial</a> that shows you how to use an ATTiny85 or ATTiny45 as a lightweight 'Arduino'. </p>

<p>Recently, I have <a href="https://electronics.stackexchange.com/questions/136919/attiny-project-resets-when-plugging-in-phone">tried to use an ATTiny13A</a> for a project, but that one only has 1KB of flash memory, which leaves you with hardly any space for the Arduino bootloader, let alone your program, so therefor I chose to program it directly using AVR Studio, at which point I think you cannot in any way call it an Arduino project anymore. :) Still, it's not that different. You only miss out on some of the library functions, and the implied application loop.</p>
 4969: <p><a href="http://digistump.com/products/1">Digispark</a> comes to mind, or any of the <a href="https://www.tindie.com/products/bot_thoughts/eezeetiny841/">ATTiny</a> <a href="https://www.tindie.com/products/bot_thoughts/eezee-tiny-breakout-programming-board-kit/">breakout</a> <a href="https://www.tindie.com/search/?q=attiny">boards</a> at Tindie. Or, make your own PCBs, I just now finished soldering a few ATMega328p circuits to <a href="https://www.tindie.com/products/ptudor/jemma-clock/">boards I designed</a>. Microcontroller is $1.50, PCBs range from $2 to $8 each, time is "free."</p>

<p>Also consider <a href="http://www.ardueasy.com/2014/10/different-varieties-of-arduino-nano.html">"compatible with" designs</a>; while you're not directly supporting the ecosystem, if you've already paid full price once and your conscience is clear, eBay has plenty.</p>
