30 Places to Find Open Data on the Web by Romy Misra.
From the post:
Finding an interesting data set and a story it tells can be the most difficult part of producing an infographic or data visualization.
Data visualization is the end artifact, but it involves multiple steps – finding reliable data, getting the data in the right format, cleaning it up (an often underestimated step in the amount of time it takes!) and then finding the story you will eventually visualize.
Following is a list useful resources for finding data. Your needs will vary from one project to another, but this list is a great place to start — and bookmark.
A very good collection of data sources.
From the comments as of April 10, 2012, you may also want to consider:
(The photography link in the comments is spam, don’t bother.)
Other data sources that you would suggest?