I think little bits of me seep into my works sometimes, but I have never intentionally written about something that has happened in my life. In fact, most of what I write is so far removed from my day to day life that I'm having a hard time thinking of anything major that I could work in... hmm...
As for the "write what you know" discussion, well, I've never attended Hogwarts, and I'm not a mutant... so that is obviously out. But, I have been in love, I have had sex, I have been in long term relationships, and those themes pop up quite often. So yes, I do write what I know... and then I connect it to whatever has popped into my head.
... Now obviously the MSV girls are an exception to this, but that's just a light hearted connection... or at least, it started out that way... hmmm...