Easy way to dismiss keyboard?

Try:

[self.view endEditing:YES];

You can force the currently-editing view to resign its first responder status with [view endEditing:YES]. This hides the keyboard.

Unlike -[UIResponder resignFirstResponder], -[UIView endEditing:] will search through subviews to find the current first responder. So you can send it to your top-level view (e.g. self.view in a UIViewController) and it will do the right thing.

(This answer previously included a couple of other solutions, which also worked but were more complicated than is necessary. I've removed them to avoid confusion.)

You can send a nil targeted action to the application, it'll resign first responder at any time without having to worry about which view currently has first responder status.

Objective-C:

[[UIApplication sharedApplication] sendAction:@selector(resignFirstResponder) to:nil from:nil forEvent:nil];

Swift 3.0:

UIApplication.shared.sendAction(#selector(resignFirstResponder), to: nil, from: nil, for: nil)

Nil targeted actions are common on Mac OS X for menu commands, and here's a use for them on iOS.

To be honest, I'm not crazy about any of the solutions proposed here. I did find a nice way to use a TapGestureRecognizer that I think gets to the heart of your problem: When you click on anything besides the keyboard, dismiss the keyboard.

1. In viewDidLoad, register to receive keyboard notifications and create a UITapGestureRecognizer:

   NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
   
   [nc addObserver:self selector:@selector(keyboardWillShow:) name:
   UIKeyboardWillShowNotification object:nil];
   
   [nc addObserver:self selector:@selector(keyboardWillHide:) name:
   UIKeyboardWillHideNotification object:nil];
   
   tapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self
   action:@selector(didTapAnywhere:)];
   

2. Add the keyboard show/hide responders. There you add and remove the TapGestureRecognizer to the UIView that should dismiss the keyboard when tapped. Note: You do not have to add it to all of the sub-views or controls.

   -(void) keyboardWillShow:(NSNotification *) note {
       [self.view addGestureRecognizer:tapRecognizer];
   }
   
   -(void) keyboardWillHide:(NSNotification *) note
   {
       [self.view removeGestureRecognizer:tapRecognizer];
   }
   

3. The TapGestureRecognizer will call your function when it gets a tap and you can dismiss the keyboard like this:

   -(void)didTapAnywhere: (UITapGestureRecognizer*) recognizer {    
       [textField resignFirstResponder];
   }
   

The nice thing about this solution is that it only filters for Taps, not swipes. So if you have scrolling content above the keyboard, swipes will still scroll and leave the keyboard displayed. By removing the gesture recognizer after the keyboard is gone, future taps on your view get handled normally.