Now, the fun part. Break out the maps. Libraries are good sources of maps and atlases in a variety of sizes. Make 20 copies of a small world map.
UT Library Map Collection
Outline Maps at Houghton Mifflin
Outline Maps at About.com
United Nations Cartographic Section
National Geographic's Map Machine
CGRER - U of Iowa's Center for Global & Regional Environmental Research
Dr. Jay's Page on Maps
World66 Map Countries Visited
Finding Your Way with Map and Compass
How far is it?
Test your Geography Knowledge
NASA's World Wind 3D demographic program
Comparison of World Wind and Google Earth
Earth From Space
See the section Travel, Map & Outdoor Gear Catalogs at the end of the guide for more map links.
"Categorize the countries/cities: 1 = always wanted to see, 2 = neutral, 3 = never want to see. Now, put this map/list away to reference AFTER you return home from your RTW trip, so that you can see for yourself just how much you have changed." <Alan Nelson>
Identify all the destinations you would like to go to, then start reading to get more ideas. Try not to confine yourself, or impose limits based on the areas you are familiar with. You may be surprised at how many places get added to your list as you become more familiar with travel literature. Take into consideration whether you will be planning adventures, like diving, rafting, skiing, desert treks, or rainforest hikes. Resist the temptation to start connecting the dots :-)
The quickest and easiest way to research countries is to go to the library or bookstore and read the Lonely Planet's introductory sections. The book does a good summary in the sections called "Highlights" and "Suggested Itineraries". This will give you a good idea about a place, and help narrow things down. There is no need to read the rest of the book until you are on the road.
Unless you are going to be in a place more than a month or two, you will usually be on the tourist trail. The common tourist routes are common for a good reason, they follow convenient paths to worthwhile places -- the trick is to ignore the tourists! The notes online at LP were very useful a couple of times, but tend to be incomplete, or the information you need is already in the book. Also, the great majority of people you talk to on the road will only know what is in the LP, so don't expect too many unique tips from them, unless you are in uncharted territory. Trust yourself -- make your own plans.
Some Popular (Heavily-Touristed) Stops: New Zealand, Australia, Bali, Singapore, Bangkok, Hong Kong, Nepal, Taj Mahal in Agra, Kenya, Egypt, Greece, Rome, Florence, Venice, Paris, Amsterdam, London, New York, Washington D.C., Orlando, San Francisco, and Hawaii.
"South Asia (India, Pakistan, Nepal, Bangladesh, Sri Lankan, etc.) -- because of the special role of English, among other factors -- is one of the easier areas in Asia in which to travel. The biggest common mistake of travellers who spend lots of time in India is overlooking Pakistan, which is a huge part of what was India and where Moghul architecture can be better appreciated in cultural context. Notably more difficult are Russia (the largest country in Europe and Asia), China, and the countries of Central Asia, among places I have been. I have not travelled in most of the Asian countries west of India (only Pakistan), but I suspect travel throughout West Asia (Iran, Iraq, the Arabian Peninsula, Kurdistan, Afghanistan, the Caucasian and Trans-Caucasian states, etc.) is not easy. Travel in most of Africa is generally regarded as harder than Asia." <Edward Hasbrouck>
"Try not to concentrate on cities too much. There are few really unique and interesting cities in the world (Paris, Istanbul, Fez, and Hanoi stand out as examples). In the Third World, cities are often hasty affairs of concrete and cinderblock. To see the traditional life of most of the world you must travel to the towns, villages, and countryside." <Larry Lustig>
Avoid big cities, basically they're all the same. Use tuk-tuks, rickshaws, and taxis as much as possible in big cities to get your business done and leave -- the pollution, disease, and driving can kill you. Save the tourist sights in a big city for a second visit if you have to return to that city -- sometimes it is hard to leave the big cities.
If you haven't seen NASA's Earth at Night poster, then have a look at these links. Compare it to a map and see if it meets up with your expectations.Earth at Night
NASA GSFC Astronomy Picture of the Day
NASA JPL PhotoJournal - 3 MB version
NASA VisibleEarth - different formats and sizes.
JSC Digital Image Collection FAQ
3-D Animation with Fires
Earth and Moon Viewer (similar)
Google Earth TimeLapse
Columbus Guides' World Travel Guide
CIA World Factbook
US State Department's Background Notes
Library of Congress' Country Studies & Area Handbooks
Index of Economic Freedom
Bug Bog Travel Guide
SE Asia Border Crossings (see Low Res border map)
Festivals and Events
Earth Calendar - Holidays
2-Camels World Festivals & Events
UNESCO World Heritage List
Wonders of the World
Museums Around the World