This site is the one I tend to read most regularly for information and updates on what's going on in the parks, and how to make the wisest use of the NextGen systems. I appreciate the first-hand, up-to-date information and personal accounts, and the forums are extremely well-moderated, which makes for mannerly and informative discussions.
If I'm trying to figure out when to visit or want to browse through accounts of recent park visits, I check out yourfirstvisit and easy wdw. In selecting a week, I keep in mind the historical discounts offered at that time of year, as well as current discounts, for which I turn to mousesavers.
When we were visiting during the Food & Wine Festival, I spent some time on the Disney Food Blog, to familiarize myself with the food kiosk menus and get reviews of the various offerings.
When it comes to formulating touring plans, or if I want to see where to get a certain food item or what section of a resort to request, I use the personalized touring plan evaluator, room finder and menu search tools on the touringplans website (I had to pay a few dollars when I joined.) (Restaurant menus are also available here on wdwmagic site, in the Dining information section.)
If I want to see if the Disney Dining Plan would be a good deal given the restaurants we're interested in visiting (it never is, but I like to check), I use the distripplanner website.
Now if you want resort-specific sites.......There's some great sites for that, too.