I'm going to be working on a project from a DC power supply, and I need to know the maximum current the Raspberry Pi can handle from the USB port. I know my wall wart adapter that came with my Pi outputs 5volts at 1000mA, but how high can I crank up the amperage without destroying my Pi?
Current (amperage) doesn't work like that. The device draws the current it requires, and the power supply needs to provide that or higher. For example, if you were to switch to a 2A (2000mA) supply, it would operate fine (assuming 5V of course).
So the answer is there is no limit. Just make sure you provide the appropriate voltage and at least the actual current the Pi (and any attachments) will require.
there's a short-circuit protection polyfuse, that's supposed to trip when the current drawn from the power supply exceeds 1.1A (constant, or a little bit higher for the short bursts). considering the RasPi consuming about 0.7A, your project may safely draw about half-an-ampere.
if you shorten the polyfuse, you may get higher currents, provided your power supply can handle them, but you may eventually burn and damage PCB tracks depending on how high you'd go.
also, earlier versions of RasPi included separate 150mA polyfuses for every USB port, you may check for these if your board is not a recent one.