Data360, a site where you can find, present and share data; created to provide clear context on important cultural, environmental, social and economic issues.
FlowingData, explores how designers, statisticians, and computer scientists are using data to understand ourselves better - mainly through data visualization.
Hohli, an on-line chart builder.
IBM Many Eyes, a shared visualization and discovery service.
Selected List of Recommended Visualization Tools from datavisualization.ch