First time: about two months salary. I'd just been laid off for the second time in two years, and rather than find another job in the same industry, I decided to try doing my own thing for a while. It was a great learning experience and I eventually came out ahead, but I basically lived month to month for several years.

Second time: about a year's salary in savings, and I had enough revenue to live on by the time I quit my day job. I was probably overly cautious, but my wife was pregnant and I didn't want to blow it.