Biking around Europe, long popular with the natives, is gaining in popularity, and is a great way to go if you have the time, equipment and energy. Small, flat countries like Denmark, Holland and Hungary are the best options. Issues such as health and weather play a bigger role for bikers than for other travelers, of course, and biking will not be as casual an affair as other modes of transport. There are several books specifically about biking, both Europe-wide and for specific countries. They all give plenty of details and tips for bikers. Best bet is to just Google "bike europe" and see what the latest information is.

If you do not want to ship your own bike over, it is easy enough to pick up a good bike for a reasonable price there, especially in Holland and Belgium. For short distances, you can often rent bicycles at the train station for a few dollars a day, and come and go as you please. This is a really nice option to escape the chaos of a town like Amsterdam.

Companies such as Ekilib (http://www.ekilib.com/) offer various bike tour packages, and you can look for the book "Europe by Bike" (the fourth printing was in 1999) or check in with http://www.biketrip.org/.