Rome2rio - Discover how to get anywhere by plane, train, bus, ferry and automobile. Nomadic Matt - Guides on how to travel cheaply in over 60 different countries. The Savvy Backpacker - Guides on how to travel cheaply specifically in Europe. TripAdvisor - Traveler reviews on everything from museums to restaurants to hotels.
City Maps 2Go (iOS/Android) - Smart phone app that allows you to download maps and use them offline.
Kayak - Shows cheap flights from different carriers and has an "Explore" feature where you can see a map of the world and the cost to fly anywhere on a specific date. Skyscanner - Compares flights to find the cheapest available.
The Man in Seat 61 - Extremely in-depth guides on train travel anywhere in the world. Eurail - Eurail Passes are train passes for most trains in Europe and only available to non-European citizens. There are many different options available varying by length of time, amount of travel, country, and region.