An ATMega168 might run you a whole $5 tops. I know it's not the ATmega32 you were looking for, but it is common and also can be used in the $50 robot tutorial. You will need a programmer, which you will be able to use for nearly any project using Atmel microcontrollers. That will run you about $35.
I know how it is to be on a tight budget and salvaging components is a good way to offset the cost of consumables, like resistors, capacitors, etc., but there are some things that you will end up having to purchase. In the long run, the investment will be worth it.