3DEP data from the USGS (which has superceded the National Elevation Dataset (NED)
Access through The National Map .
Raster resolution is 1 arc-second (approximatelly 1 point every 30 meters) and 1/3 arc-second (approximately 1 point every 10 meters) for most areas. Some areas have higher resolution data, at 1/9 arc-second (1 point every 3 meters), including SE Michigan. Data for Alaska is at a different resolution.
Contours are available at a scale of 1:24000. This is suitable for mapping at somewhere around the size of a neighborhood or town. Contours at this scale will not be detailed enough for small areas, like a city block, and will have too much detail for representing topography over larger areas. For smaller areas, try downloading raster data at the 1/3 or 1/9 arc-second, and deriving your own contours. For larger areas, a number of approaches can work, including contours available from The National Map at the 1:1million scale (see the Small-scale Datasets section).
Local governments (state, county, municipality) may have additional higher-quality data that is not available from The National Map, and these can included LiDAR-derived DEMs, more detailed contours, or other forms of data.
ASTER GDEM
http://www.gdem.aster.ersdac.or.jp/
http://www.nasa.gov/home/hqnews/2011/oct/HQ_11-351_ImprovedTopoMap.html
You can download data from the REVERB/ECHO viewer - really great global resolution!
SRTM
SRTM data is only available for areas between latitudes 60 S and 60 N.