Wikipedia. For Travel. Everything you need to know in one place.
WikiTravel is my go-to guide when traveling, simply because it has the most comprehensive and concise information and includes cultural information. Trip Advisor is great for specific restaurant recommendations or hotels, but WikiTravel should be your guide book for what reputable tour companies to use, ways to get to/from the airport, what the tipping etiquette is... etc. Every article is organized by the following structure:
Understand (overview of the region, history, climate, districts...)
Get In (plane, train, automobile and more...)
Get Around (public transportation, rental car companies...)
See (main landmarks, recommended itineraries)
Do (activities and entertainment)
Buy (shopping, expected costs, bargaining tips)
Eat (local dishes, recommended restaurants)
Sleep (hotels and hostels)
Stay Safe (neighborhoods to avoid, scams, emergency contact info, etc.)
WikiTravel surpasses TripAdvisor in it's explanation of cultural norms and suggestions for avoiding conflict or offenses. In the "buy" section, it'll explain if it's appropriate to bargain and how to go about doing so. In the "stay safe" section, it'll caution against things that could offend people or get you into trouble. Tips like this make WikiTravel a great, consolidated resource when planning your next trip.
Get In & Get Around
The other more useful sections of WikiTravel are "get in" and "get around", which detail all the ways of getting to and from your destination. For example, they'll list what options you have for getting to and from the airport and the various costs. It is a great aggregator of all your transit options with helpful advice and cost.