Ancestry.com posted a new database on their site, apparently today: United States Mortality Schedules (and Index) 1850-1880). This database is incomplete and is still in progerss, users should read the description to be certain what locations are covered. Not all of these schedules are extant, either. This is a welcome addition to Ancestry.com's set of databases. We'll be posting more about this as time allows.
The 1850-1880 United States Mortality Schedules can be searched here.