I prefer my backpack carrier called the "dog gone" carrier. We use it for bike riding and x-c skiing, and it is the BEST pet-related purchase I have made. It is not a totally enclosed carrier (like for airline travel ) because the pet's head is sticking out. Like the manufacturer says, it is the first carrier designed for the enjoyability of the dog, and I believe it.
You can buy them at a bunch of places--just do a google for Dog gone carrier. Here is one place with a good photo....
http://www.valleyvet.com/ct_detail.h...2-00b0d0204ae5