This one is from Tilley. This page displays a 2.6k static gif first. The 29k animated gif loads only after rest of the page has loaded.

		HTML:           0.9k
		Static Gif:     2.6k
		Animated Gif:  28.6k
		               -----
		TOTAL:         32.1k
		

Page Sizers will report about 3.5k.

Note that this technique does not work on IE3, WebTV, Opera, or any browser without JavaScript. It works fine with IE4, and Netscape 3 & 4 though.