A server side image map can be found at The Merck Company Site Map. It's a good thing that the map was nicely labelled since the links were so long it was not even possible to read the coordinates.
This side also has an excellent (my opinion) example of the use of LOWSRC on The Merck Company Home Page

Two interesting client side image maps are AT&T and Hewlett-Packard.

	Original background image 16,411 kb
	35% reduction using 96 color palette
	30% reduction using 128 color palette
	44% reduction using 64 color palette
	52% reduction using 32 color palette
	62% reduction using 16 color palette
	57% reduction - Dithered Browser Safe Palette