This is exactly my goal as well. I'm currently working a full time job, moonlighting contract jobs on evenings/weekends, with the goal to save enough money to cover my expenses for 6 months. After that I plan to go into full time consulting and specifically target shorter term contracts and take off blocks of time in between. I've always seemed to work best in spurts and software development (new projects anyway) are a good industry for this type of environment.