Great breakdown of which types of visualizations to use for data.
data
From data to Viz
Mockaroo
Mockaroo lets you generate thousands of rows of realistic test data in CSV, JSON, SQL, and Excel formats.
Kaggle
“an arena where you can match your data science skills against a global cadre of experts in statistics, mathematics, and machine learning. Whether you’re a world-class algorithm wizard competing for prize money or a novice looking to learn from the best, here’s your chance to jump in and geek out, for fame, fortune, or fun.”
Foursquare Venues, Wikipedia Articles, Census Data and More… All With Just an IP Address! | Infochimps Blog
Our Mobile Planet
“provides insights into smartphone usage and mobile attitudes. Use it to create custom charts that will deepen your understanding of the mobile consumer and support data driven decisions in your mobile strategy.”