I think the only time I’ve gone to a travel agent was to get a tourist visa approved. Otherwise, I’ve planned most, or maybe even all of my trips using these websites listed below. They’ve helped me tremendously and perhaps they will for you as well.
With so many sites offering a crazy combination of flights or hotels or both, I do expect that this list–that has already changed over time–will keep continue to change. Some I’ve simply removed (like Frommers or Bootsnall) because they don’t seem as relevant as they were back in the day.
Great sites that I normally go to:
Lonely Planet (typically not as informative as their printed guides, but good for basic facts, especially if one is a quite the self-proclaimed travel-idiot of any country)
Expedia (I’ve found out in recent years, that they do great flight-hotel bundles. Fantastic for short breaks which only involve a single location to bed down)
Lonely Planet’s Thorntree Forum (A place for you to ask questions and more questions. They even have neatly separated folders and threads according to countries!)
Trip Advisor (Read the reviews about accommodation. Interesting to see the amount of information discrepancy the hotel websites give and the people who stayed there. Arse-saving, in my opinion.)
Accommodation Booking links
I used to include hostel-links here, back in the day when accommodation sites weren’t as consolidated as they are now but these could actually be found in Tripadvisor and Expedia these days.
Now what have I missed out?