All my standalone Arduino’s on one page. Also see the Raspberry Pi connected ‘Duino’s.
Each has been tested by compiling and uploading the standard Blink program or a variant.

Tested with the Arduino 1.6.5 on Windows 8.1 except the Freaduino tested on the Raspberry Pi!

Uno ATMEGA328 R2, R3

All are cheap but well made clones from China. All but one worked fine the first time. One, a Funduino, had a damaged bootloader, repaired with the excellent Bootloader program by Nick Gammon. And that Uno is fine now also!

Mega 2650 ATMEGA2650

with a prototype baord and case.

Freaduino MEGA 2650, ATMEGA2650 3.3V/5V switchable, high power output.

Has a fake FTDI IC, which got bricked by a FTDI driver in 2014.
I got it repaired on a  Raspberry Pi . Impossible to upload to at the moment from Windows due to missing working driver but works fine connected to a Raspberry.

I have a separate post how I revived this board!

Does not exactly the same dimensions as the MEGA 2650, the prototype shield does not fit. 

Nano ATMEGA328

Pro Mini ATMEGA328

Pro Micro ATmega32U4

Install in Arduino IDE 1.6.5. On the tutorial page there is an example sketch, Blinky, that  blinks the TX and RX leds.

Digispark ATTINY85 USB

Install in Arduino IDE with this tutorial. Requires Arduino IDE 1.6.5. The wiki page contains the example program: a variant of blink!