What To Look For
Ski boot bags are available in a variety of types. Some are daypacks that have straps so you can strap the boots to the outside of the pack. Most are essentially big boot-shaped bags that you slide your boots into, then zip and carry like a shoulder bag or a backpack. Some are rolling luggage type setups. Only the rolling luggage types are designed to carry more than one pair of boots. Decide on your needs; if you are traveling by air, the rolling luggage types simplify things. If you just need a bag to carry boots in the car, a simple duffel style is adequate. If you are going to be carrying them for any length of time, the backpack style is the best. When looking at ski boot bags, bring your boots and make sure they fit into the bag.
Common Pitfalls
Don't just buy the first bag that catches your eye. Check the zippers to make sure they are a durable construction. Check the quality of stitching. Also load the bag with your boots and make sure you like how it carries. Ski boots weigh a lot, and the bags that just have a handle, while cheap, generally don't carry as well as backpacks. Backpacks might not fit your torso, so check that before buying.
Where To Buy
Ski boot bags can be found at ski specialty shops. Many online dealers carry them as well.
Cost
As of September 2009, ski boot bags vary in price from around $40 for basic bags to $60 for backpack style to $170 for the rolling luggage style.