Freebies on ancestry that I know of:-
http://www.ancestry.com/search/rectype/census/uk/default.aspx?
or
http://www.ancestry.co.uk/search/rectype/census/uk/default.aspx?

1881 England Census (images, every name index) - Free Index
1881 Wales Census (images, every name index) - Free Index
1881 Isle of Man Census (images, every name index) - Free Index
1881 Channel Islands Census (images, every name index) - Free Index


http://content.ancestry.com/iexec/?htx=List&dbid=6742&ti=0&r=0
1880 United States Federal Census

Social Security Death Index and free on Familysearch too
http://www.ancestry.com/search/db.aspx?dbid=3693


http://www.ancestry.com/search/rectype/vital/freebmd/main.htm
England and Wales, Civil Registration Index: 1837-1983
many prefer http://www.freebmd.org.uk
which is the latest build of this database - but has smaller limits of search size.