Enigma.io is great for public data too.
Quandl (https://www.quandl.com/browse) is similar to Engima, except they got rid of all the fun datasets and added more finance/economic datasets. Hmrph.
the remaining 50% of datasets have a lot of gems
quality in the breadth of data is important
state-wide liquor license, corp reg. OSHA is great data. AMS shipping records. FDA adverse events. Oil and Gas well locations/production. Consolidated weather reports since 1800... im almost certainly forgetting some.