I find that reading fiction on vacation really stimulates my programming brain. There's a lot to be said for letting your mind roam free for a bit. I believe PG talks about the value of letting your mind roam in one of his essays (or possibly Hackers and Painters). In particular, I've found Neal Stephenson's books to be great for this purpose. If you haven't read Cryptonomicon, Snow Crash, or Diamond Age, I would suggest reading one of them. It will satisfy your need for some "geek" content on vacation, without being all business.
