Sounds like you have a pot with an "audio taper". A simple way to correct (without fancy math) is to characterize the pot. Set it to the 0-degree setting (all the way counterclockwise), take a reading, store it in a spreadsheet. Turn the pot to 10 degrees, take a reading, store it in the spreadsheet. Continue all the way around.
Now, turn this spreadsheet around. Store it in an array in your code, then whenever you get a reading, look it up in the table (you'll have to look between two nearest values) and the index into the table is the linearized return value.
The Gadget Shield
: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons