Sometimes you would want a shadow on a view.

Easiest and quickest way is to just add it on the view's layer:

-(void)loadView {
    CGRect frame = [[UIScreen mainScreen] applicationFrame];
    self.view = [[UIView alloc] initWithFrame:frame];
    self.view.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
    self.view.backgroundColor = [UIColor blackColor];
    UIView *glowView = [[UIView alloc] initWithFrame:CGRectMake(frame.size.width /2 -10, frame.size.height /2 -30, 20, 60)];
    glowView.autoresizingMask = UIViewAutoresizingFlexibleBottomMargin | 
                                    UIViewAutoresizingFlexibleTopMargin |
                                    UIViewAutoresizingFlexibleLeftMargin |
    glowView.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:glowView];
    //Setup the shadow on the view's CALayer.
    CALayer *viewLayer = glowView.layer;
    viewLayer.shadowOffset = CGSizeMake(0, 0);
    viewLayer.shadowColor = [[UIColor yellowColor] CGColor];
    viewLayer.shadowPath = [UIBezierPath bezierPathWithRect:glowView.bounds].CGPath;
    viewLayer.shadowRadius = 10.0f;
    viewLayer.shadowOpacity = 1.0f;
    //Let's animate it while we're at it.
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"shadowOpacity"];
    animation.duration = 0.5f;
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    animation.fromValue = [NSNumber numberWithFloat:1.0];
    animation.toValue = [NSNumber numberWithFloat:0.0];
    animation.autoreverses = YES;
    animation.repeatCount = HUGE_VALF;
    [viewLayer addAnimation:animation forKey:@"shadowOpacity"];

I must admit, this is kind of basic stuff. But it seems a lot of people actually forget about the fact that all UIView subclasses are based on Core Animation CALayers.

See the source code and try the example, the interesting bits about this example are all contained within the fourth tab of the application, it's the XSDFourthViewController in the code.