[QUOTE=Asimovian]
I was recently introduced to this game, and I’m absolutely head-over-heels in love with it. It is long enough and involves enough strategy to keep it interesting, but not so involved that I get frustrated (I don’t have the patience for a lot of strategical games). And, of course, one never really gets tired of saying, “I’ve got wood for sheep!” (One wonders if Hal Briston has given the game a try…) 
In poking around on Amazon, I’ve noticed that there are numerous variations and expansions for the game. I’m just wondering whether anyone here has invested in any other versions of the game, and how they compare to the original. Your thoughts?
[/QUOTE]
Welcome to the world of Catan :). It is always a great game to teach, because the look on new players faces reminds me of how much I loved it when I first learned. And playing in college, there is no shortage of the number of euphuisms that come up. Settlers is on the short list of my favorite games. A good part of it is that I can play it with people who aren’t quite as competitive as me. I have played the base game (with and without 5/6 player expansion), Seafarers, Cities and Knights, Starfarers, and the card game + expansion.
Seafarers and Cities and Knights are the base expansions. That is, both of them require the base game to play, and come with pieces to add on to the board. Mayfair has just released an updated version of the base game, Seafarers, and Cities along with 5 and 6 player expansion. The rest of the expansions are stand alone games
Seafarers adds the concept of ships, which act similarly to roads, except you can move them. Instead of one island, there are multiple ones that you can settle and explore. There are a number of starting scenarios to choose which dictate how the game will be played. It does a good job of capturing the feel of Settlers, while expanding your options.
Cities and Knights introduces more direct conflict into the game. Some people don’t like it as much, because it does make it more competitive.
Starfarers is a stand alone game. I recently bought it, because they stopped making it. I eventually want to get every Settler’s game, so ones that will be hard to get later go to the top the list. I have only played it once thus far, but it is pretty awesome, and it has the best dice roller of any game I’ve ever played. The pieces are fragile though, and prone to breakage. The game plays like Settlers in space, with a few new interesting concepts.
The card game is alright, but I’ve found it to be less interesting and more time consuming then the base game. But since Mouse and I are only 2, it gets played a lot more often then everything else.
You might be interesting trying other European games well. A lot of them have similar balances in terms of strategy and competitiveness. Carcassonne is another game that we have most expansions to and it has the advantage of being playable as a two player game.