Here are some useful travel resources:
Booking.com – Best place for finding hotels and other types of accommodation. They have a huge selection in most cities.
Airbnb – If you don’t want a hotel or a hostel, but prefer a local holiday apartment, this is where to look.
Skyscanner – The perfect site to use if you’re looking for cheap plane tickets for your trip. Even if you don’t know where you’re going yet, you can get suggestions through Skyscanner and see where it’s cheapest to fly to.
Expedia – A travel site where you can search for a bit of everything. Cheap flights, nice hotels, car rental according to your needs. You get the option to book a package of everything with a possibility of an overall discount.
Wikitravel – Further information on all sorts of destinations around the world.