Traditional publishers are trying to compete with online services, and there are many dictionaries and encyclopedias out there trying to figure how to survive in the age of Wikipedia. Some established dictionary publishers have decided to put their tools on the web for all to use.
Larousse.com has 5 of its French dictionaries of various flavors, as well as translation dictionaries and its encyclopedia all available for you to use. The interface is easy and clear, and there are hyperlinks from article to article and between works. The encyclopedia does have user-contributed content, which is identified as such. http://www.larousse.com/
Treccani, the publisher of the Enciclopedia italiana and the unfinished Dizionario biografico degli italiani, has decided to put them up on the web. The biographical dictionary had been plodding along very very slowly, and one hope is that users will contribute to entries so that it finally arrives to the letter "Z". The site also has access to a wide variety of Italian dictionaries, and a nice widget that you can download to your toolbar that allows you to search either in a dictionary or its online encyclopedia. Moreover, from the encyclopedia entries, you can double click on each word to get to its definition. The site is pretty cluttered, but the search boxes (vocabolario and enciclopedie) should be obvious. http://www.treccani.it/Portale/homePage.html
There are many similar initiatives. Others of special notice are Garzanti linguistica (free with registration), and le Grand Robert online, for which Stanford has a subscription.