Settlers of Catan has dozens of editions to choose from. You can buy the original, a Star Trek edition, a board that looks like your state...etc. etc. Stepping away from map variations comes a new version in the form of Settlers of Catan: Compact Edition. It's everything you love about Catan, but in small travel size form! Having played it a couple times with friends, I have to say it's my preferred way to play.
In style, it's not at all different from regular Catan, just smaller. The cards are about a fourth of the size of regular cards, and the pieces and board are of course miniature as well. Cards have a convenient holder for handing out resources, and all four players' pieces fit snugly in slots below the plastic game board. The settlements, roads, and cities all can be placed in fixed pegs as to better cope with the bumps and turns in the road, and if you're limited on players, there's even a separate set of rules for a two player game!
Obviously this is the version you want to use if you're traveling in a car, train, or plane...but why would you even want to play Catan in such a situation? Time. So many games of Catan are ruined by players whose greed and lack of bargaining cause the game to drag on for hours at a time. When you're on the road, you've got nothing but time, and it really changes the dynamic when you've got nothing better to do than wait! The ability to have a one-on-one game is certainly a plus, and the rules aren't that much different!
There is a rather small flaw in that not every tile is removable, but rather multiple tiles are fixed in puzzle form. The game variety can still be changed in multiple formats, but not nearly as many as a standard board. Another small gripe is the miniature dice kit needs a good shake to truly get a random roll. There were a couple times a quick flick of the wrist gave me the exact same roll as the person before me.
Bottom line is this is something you should own if you want to play Catan on the road, or even on vacation and are scared of losing pieces to careless cousins. If you're interested, you can get it online here.