Our last two big trips were completely booked online:
-Backpacking trip to Italy --- we stayed in a mix of 3 star hotels and hostels.....all booked online. We also booked our airfare and train pass online
-Month in Africa --- the entire trip was booked online with an African travel agency (located in Nairobi, Kenya). Airfare was booked online by me.
I highly recommend booking online if you have the time and patience to do the research --- a couple of times, I went in to a travel agent to see if they could beat the online prices, and they never could.