Richard's Monopoly
Includes a list of Richard Wilding's collection, as well as links and a wanted page for buying and selling items.
http://richard_wilding.tripod.com/monopoly.htm

Monopoly Lexicon
Photographs and literature for collectors. Also features an index of country-specific game editions.
http://www.muurkrant.nl/monopoly/index.html

Probabilities in the Game of Monopoly
Includes land on frequencies, expected earnings, and payback times.
http://www.tkcs-collins.com/truman/monopoly/monopoly.shtml

Monopoly Rents
A table of costs and various rents in the UK version of Monopoly.
http://www.jdawiseman.com/papers/trivia/monopoly-rents.html

Monopoly.com
News, merchandise, history, tournaments.
http://www.hasbro.com/monopoly/

Durango Bill's Monopoly Probabilities
Statistical and graphics data for End-of-turn, Land-on, and per-dice-roll Monopoly probabilities.
http://www.durangobill.com/Monopoly.html

PSMonopoly.com
Features calculator tools to determine a player's net worth based on the properties they own, and also a tool that calculates the probabilities of landing on certain properties based on where the player is starting.
http://www.psmonopoly.com

Monopoly Collector
Game history, facts about different versions, site owner's collection, official rules, and some sales.
http://www.monopolycollector.com/

Monopoly Man
Presents a description of the game pieces, an overview of the rules, and the game's history. Also includes commentary on variants, offshoots, and spinoffs.
http://www.monopoly-man.com/

About.com
Annotated links to a variety of Monopoly resources, including where to play online, the game's history, and information for collectors.
http://boardgames.about.com/msub19.htm

Dribbleglass.com - Monopoly Cards We'd Like to See
Spoof pictures of Community Chest and Chance cards.
http://www.dribbleglass.com/monopoly/

CNN Money: Monopoly to roll the dice and change its board
News article describing the new Then and Now edition of the game.
http://money.cnn.com/2006/04/24/news/funny/monopoly/index.htm

Squidoo Monopoly
Seth Godin's opinions about what's wrong with Monopoly. Offers rules variants reflecting those opinions.
http://www.squidoo.com/monopoly/