Simple example of drawing a drop shadow with Core Graphics.

iPhone: Drawing a Drop Shadow

- (void)drawRect:(CGRect)rect
{
    [super drawRect:rect];

    rect = [self bounds];

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSaveGState(context);

    // use the same background color as the view, but with an alpha of 1.0
    const CGFloat * colorComps =
        CGColorGetComponents(self.backgroundColor.CGColor);
    CGContextSetRGBFillColor(context, colorComps[0], colorComps[1],
        colorComps[2], 1.0);

    // set the shadow
    CGContextSetShadow(context, CGSizeMake(0.0, -5.0), 10.0);

    CGRect rectToDraw = CGRectMake(
        rect.origin.x,
        rect.origin.y,
        rect.size.width,
        rect.size.height - 30.0);

    // draw the rect, including the shadow
    CGContextFillRect(context, rectToDraw);

    CGContextRestoreGState(context);
}