Further or Farther?

So what exactly is the difference between 'further' and 'farther'? Being a native-born English speaker you think I would know the answer to this question. Yeah, wrong again! I had to consult WikiAnswers for this one. And I'm glad I did cuz now I know the difference and I'm going to share it with all of you that care:

Further is used in conjuction with the word "more", meaning exactly that...more. Farther is a function of distance.

Examples:

I want to further my career. (That's just an example, it's not me saying that!)

How much farther do I need to run to get to the finish line?

The farther I travel down this road the further behind schedule I get.

So there's your lesson for today! Any more questions, just ask, I'd be more than happy to help!