www.mouser.com
Mouser Electronics. Been using these folks for years. You can get all kinds of electronic replacement parts here. I recently purchased a $3.00 control relay from them to fix a dryer control board that would have cost hundred$ of dollar$ to replace.
www.repairclinic.com
A great place for replacement appliance parts.
www.obd-codes.com
Is your Check Engine light on? If you know the code or have a code reader ($35-$100 at an auto parts store or Wal-Mart) you can look up your own codes. If you are mechanically inclined, this is a great way to start a do-it-yourself repair.
www.howstuffworks.com
Interested in knowing more about how something works? You may not know how to fix it, but you just may be able to learn enough so that you sound like you know what you are talking about!