Another vote for the free MouseWait app. Especially since their new update last week. I found the wait times to be pretty accurate. You do need to pay attention to the last time a waittime was posted, but they are usually updated by someone else in the park on a pretty regular basis. I'm not a big fan of their forums, but there's lots of other good stuff on there for a free site. I must admit to enjoying the MouseWait radio to get a little
Disneyland music fix now and then. Don't trust MouseWait's calendar, though! They frequently seem to mess up on show times and even open and close times for the parks.
Another that I use, though not as often, is the DISBoard's app (eTicket). I like this one mostly for the maps where you can filter food, attractions, shows, and bathrooms. As much as I'd love for this one to be my favorite (go DIS!), there's just not much else I use on it and it costs too much for what you get (IMO). Sorry, eTicket!
I also surprised myself by really using the DL Dining app. It gives you fast and easy access to menus for all the restaurants and a quick link to Disney Dining's phone number. Not that it takes that long to look up a phone number, but it was handy to compare a couple of menu options and then just touch the "Call Now" button. I'd use this by looking at some menus, deciding what I was most in the mood for, and then calling for a reservation about an hour out. It was great to then walk up to the restaurant with no wait when everyone else was being told 30-40 minutes. All because I called an hour ahead to put in my name. I think this one was 99 cents.
I've used a couple of others, but they were fairly forgettable and they've been deleted.