I planned my honeymoon in Italy. While I used a travel agent for hotels/airfare, it was mainly due to the discount I received using them as I had researched everything ahead of time on my own. These are the sites which were pretty valuable:

http://tripadvisor.com/ - great for reviews of hotels, restaurants, sights, etc. Be careful with the reviews though, standards for Europeans are very different than Americans.

http://ricksteves.com/ - great for itineraries and ideas for hotels, restaurants, etc.

Also helpful, is to ask the hotel concierge ahead of time for restaurant recommendations. They can usually set everything up for you too.