Student Helmet Project

[Gryd3]

See here for an article describing how to get an arduino to run on 43uA (or less -- in the comments someone is reporting 26uA, and another 4.6uA).

Fun... not technically an Arduino but incredibly helpful anyway!
I think at this point though... the OP might as well just go straight for an AVR or PIC and forget about trying to build an Arduino Clone.
OPs decision of course, but this method requires a pre-built Arduino or other method to initially program the AVR with the bootloader... then you can begin to work on your own firmware for the chip.

 

[(*steve*)]

What is "technically" an arduino?

 

[Gryd3]

What is "technically" an arduino?

I should have watched what I said...
I consider Arduino to be a finished *product* consisting of a small board populated with a USB port and various other supporting components including (most commonly) an AVR microcontroller that has been pre-loaded with a boot-loader.
If you want to clone the board, you have an Arduino clone. If you only use the boot-loader, you simply have an AVR without any of the perks the *product* has... such as on-board USB for programming, reset button, status LEDs, or voltage regulators.
For someone wanting to introduce themselves to microcontrollers, I would suggest they either stick with the expensive Arduino product, the inexpensive clones, or they ditch Arduino all together and take a look directly at an AVR or PIC...
The biggest perk of Arduino is the ease of use. One part, program it, call it done.
Buying an AVR and loading the Arduino Boot-loader requires an additional programmer, which at this point, one of the biggest perks is lost. Sure, they can use the Arduino Flavoured IDE still, but at this point they are doing all the same work and buying an additional programmer like they normally would for a PIC or AVR anyway.

 

[(*steve*)]

ok, that's a definition.

The arduino developers give you a programmer ad part of the environment. You can use your existing arduino (by your definition) to program the boot loader onto another chip.

My definition is somewhat broader. Any chip programmed with an arduino boot loader is an arduino.

using the bare chip is not much harder than using a board. Using a arduino pro mini is practically the same as using a bare chip.