h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

This is a wonderful four-player game that I learned from my college friends, and it's a great way to avoid homework for about two interactive, mentally stimulating, highly enjoyable hours. It's a German game, but I only know the abbreviation (Seidlers, but I have no idea if I spelled that right) and I believe that it's about thirty years old. I don't own a version of the game, so this explanation will probably be a woeful amalgamation of origional rules, house rules, and expansion rules. This game is wonderful enough that I just had to shout out the news, so please feel free to add details.
The Equipment:
Nineteen hexagonal tiles representing different types of terrain: desert, mountain, hill, plain, forest, and pasture. Eighteen hexagonal sea tiles, half of which are ports. Four sets of roads, settlements, and cities in red, orange, white, and blue. Resource cards: ore, brick, wheat, wood, and sheep. Development cards: victory points, soldiers, building cards, etc. Eighteen number tiles: two through twelve, excluding seven. One robber. Two six-sided dice.
The board is generated randomly by placing the tiles together to form the island of Catan, and the number tiles are placed randomly on the resource tiles (the desert hex is barren and produces nothing).
Game play:
Refer to rule book for specifics, because I don't want to write and you don't want to read pages and pages of rules. Each settlement produces resources when the die outcome is equal to a number that appears on a hex adjacent to a settlement or city. Thus, a settlement that is on the juncture of a mountain hex with a 5, a plain hex with an 8, and a forest hex with a 2, will produce one ore on a role of 5, one wheat with a role of 8, and one wood with a role of 2. Cities produce two resources. Note that the statistical probability of rolling a 2 or 12 is low, while 6 or 8 are the most commonly producing resources. 7 has the highest probability of being roled, but brings the robber into play rather than producing resources. The robber is scary and evil unless you are the one who rolled the dice (except if you have to discard) because the robber is placed on a resource hex which cannot produce until the robber is moved. Playing a soldier card also gives you control of the robber.
The point of the game is to build new settlements and expand your settlements into cities until you have twelve victory points. Settlements cannot be built next to each other, so you must expand with roads, and all of these are bought with resources. If you don't have enough resources to build something, you trade for that resource. This is the interactive part, because you have to talk people into helping you win. This is also the part that makes the game play take a long, looooong time.
Expansion packs:
Five to six player: Catan becomes large enough to accomodate five or six players.
Seafarers: Creates mini-islands around Catan, adding ships and a pirate (same rules as the robber) to gameplay. There are about six scenarios that this can provide. Does not alter game play but gives new options for growth, and adds gold as a terrain which produces a resource of the player's choice.
Cities and Knights: Totally different game play, because forest, mountain and pasture terrains produce commodities as well as resources. Adds a barbarian who pillages Catan unless enough active knights are on the board. Very exciting.
There is also a site where you can play Settlers online, but I've never done that and don't know the URL. It somehow doesn't seem as exciting because it removes the talking aspect, but I could be totally wrong.

Wonderful wonderful game. I'm sorry the entry was so long.