Google Trips is a great fairly new product from Google for organizing all your travel info and discovering places when you go.
I rely heavily on TripAdvisor before I travel anywhere. I can get reviews on hotels I am thinking of staying in. I can see great places to eat that have good reviews and can see photos of the type of food they have on offer and how it looks. It's also superb for checking out the top attractions so that when you visit a new city or country you can check out the top landmarks and be sure you didn't miss out anything, as it's always safely stored in the top 10 places to visit. I don't tend to do any booking directly on TripAdvisor, and instead use it as a research tool.
Markus Huber made this productNot exactly what you're looking for, but maybe helpful. Pollunit simplifies the decision-making process with your friends. For example: Where should it go? When should it go there? Who has time? What is your favorite holiday destination?
Hostels have improved massively over the years. Some that you stay in now are just as good as budget hotels if not better. The only reason they are listed as hostels is because they have communal areas for self catering etc. Hostelworld is ideal for finding the best places to stay if you want to travel on a budget and not spend out too much on accomodation.
Skyscanner compares flight prices from all airlines and deal-websites (Expedia, Travelocity, Orbitz). You can use this to take spontaneous trips or to find good deals on flights (especially if you don't have a specific destination in mind. Best search options: 1) You can set it to find the month with the cheapest available flights to any desired destination. 2) You can set it to search all departure airports within a few hours of your city. 3) You can set it to search for the cheapest country to fly to. For example, if you wanted to travel to South or Central America next winter (but don't really care where as long as it's warm)... it will search all of the included countries and find you the cheapest flights!