NSString* imageURL = @"http://theurl.com/image.gif";
NSData* imageData = [[NSData alloc]initWithContentsOfURL:[NSURL URLWithString:imageURL]];

UIImage* image = [[UIImage alloc] initWithData:imageData];
[imageView setImage:image];
[imageData release];
[image release];

//or nested version

UIImage* myImage = [UIImage imageWithData: 
	[NSData dataWithContentsOfURL: 
	[NSURL URLWithString: @"http://www.mydomain.com/image.png"]]];
[myImageView setImage:myImage];
[myImage release];