It looks like Ryan Carson and the guys at Treehouse have been having some fun over the last week. They have taken a week off of normal work and thrown themselves into building a Web application in only 4 days.
There is something incredibly useful about stepping back from everyday work and doing something completely different. You will learn more in those few days than you will in months of normal work.
Admittedly we cannot all just give up our normal work for a week, but we can have personal projects on the go. This is certainly something I do and it improves my skill set while also helping inform my day job.