Preparation

SubWWWay - Pack Your Bags

The UN operational rates of exchange is a simple list of over 200 world currencies in relation to the greenback.
The Oanda Currency Converter is more fancy and flexible, allowing you to relate any two of 164 currencies on any date from 1990 through to yesterday.
The One-Stop Shop's Travellers' Check List details import and export restrictions on currencies.
The American Express, MasterCard/Cirrus and Visa locators have various snazzy ways of helping you find their offices and ATMs around the world.

Rain or Shine has five-day forecasts for 800 cities around the world.
USA Today's World Weather also has five-day forecasts for many cities around the world, as well as a colour-coded temperature map for each continent.
Weather doesn't get much funkier than Intellicast's World Wide Weather Forecasts.
If you're not heading off for another six months, World Climate can tell you the average temperature and rainfall for any time of the year just about anywhere in the world.
Landings claims to have every weather link known or dreamed about on its Weather Page.
Earthwatch caters to those for whom a forecast just isn't good enough - now you can see the clouds causing all the trouble.

Although some maps, particularly city ones, are out of date the PCL Map Collection is still a very good and easy to navigate online map library. Be warned these maps are big.
Mapquest may not be immediately user-friendly, but once you get a handle on its interactive atlas you can zoom in at street level to a lot of the world's cities.
What a great idea! Maps in the News links out to the world's hot spots.
With over 500 destinations in its database the Distance Calculator will count the kilometres for you.