Is there a simplified chart of how many amps can I get at a distance by wire gauge?
I'm not sure how helpful it is, but here's a chart that shows voltage drop at various distances. This chart shows the voltage drop across copper conductors, at 100% the allowable circuit capacity. 



This chart that shows the voltage drop across copper conductors, with a 15 ampere load on the circuit.



And one with a 20 ampere load.



If you want to do the calculations yourself, you can use the formula:

Voltage Drop = 2 * Length * Current * Resistance 

That will give you a rough approximation of the voltage drop that should be expected.

*You can look up the resistance of the conductors through the manufacturer, or use values found in the National Electrical Code.