For all you realistic terrain / heightmap fiends
Google Maps now has a 'terrain' overlay tab (at least for the US)....could be useful ?
I don't think its useful to make maps but I like it as a style for google maps as I can navigate certain areas much easier. For example I find it hard to see where the top of Italy ends and Austria starts but having the Alps there in shaded relief is handy. Finding the Grand Canyon is a cinch now.
The USGS especially the seamless server is a handy link to getting at the DEM data directly. Its been a while since I used it and I remember that you need some tools to convert it into something thats easier to use.