http://aws.amazon.com/datasets/
http://webscope.sandbox.yahoo.com/catalog.php?datatype=a
http://labrosa.ee.columbia.edu/millionsong/
https://tfl.gov.uk/info-for/open-data-users/
https://www.ncdc.noaa.gov/cdo-web/datasets
https://dumps.wikimedia.org/other/pagecounts-raw/
http://cnets.indiana.edu/groups/nan/webtraffic/click-dataset/
http://lemurproject.org/clueweb12/
http://bigdata-madesimple.com/70-websites-to-get-large-data-repositories-for-free/
https://immport.niaid.nih.gov/immportWeb/home/home.do?loginType=full
https://github.com/caesar0301/awesome-public-datasets
https://www.google.com/publicdata/directory
https://www.kaggle.com/competitions
http://archive.ics.uci.edu/ml/datasets/MSNBC.com+Anonymous+Web+Data
http://gcmd.nasa.gov/records/GNIS.html
http://www.ncdc.noaa.gov/data-access/quick-links
This quora answers the same question and is a living list: https://www.quora.com/Where-can-I-find-large-datasets-open-to-the-public