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[on:]

I have been reading some pretty conflicting statements as to the feasibility of powering an ATMega directly from USB. I know that the Arduino boards them selves take a wide range of power inputs allowing for a USB connection, and therefore power, to be granted. I am in the midst of planning my own shield/board that will need to be powered strait from a USB header off of a PC Motherboard - I have the basic ATMega328 pinouts and a pref board that I plan to use as a prototype but what escapes me is USB power... I was going to wire up a line to the proper input, but needed some clarification before hand.

If I need some sort of resistor(s), which ones? (Still very new to building my own boards and anything beyond BASIC soldering...)

[Reply #1 on:]

The USB power source is already regulated to 5v so yes you can use it directly.  The Arduino itself does the same.

[Reply #2 on:]

Thanks! Now the only question remains, do I wire the 5v line to both sides of the chip?

[Reply #3 on:]

....pretty conflicting statements as to the feasibility of powering an ATMega directly from USB...
 I am in the midst of planning my own shield/board that will need to be powered strait from a USB header off of a PC Motherboard

There is nothing conflicting about the feasibility of USB power. There is either enough of it, or there isn't.

The USB supply is regulated anyway.  So that takes care of the volts, and all you have to worry about is the current. 

If you intend to use just a few low-power peripherals, you will probably be fine, so I won't ask about the logic behind your intention.

Just be aware that, when I first encountered a power problem, it was not because I had done anything to the Arduino, it was because I had changed the motherboard in the PC.

[Reply #4 on:]

This is a good tutorial for wiring your chip:
http://arduino.cc/en/Main/Standalone

[Reply #5 on:]

Thanks! Now the only question remains, do I wire the 5v line to both sides of the chip?

Yes