All of these require submitting data to an online service. If your data is sensitive, you may be able to just upload your summary statistics.
- Google Spreadsheets Explore and Fusion Tables - Create visualizations from spreadsheets in Google Drive (or uploaded).
- Datawrapper is easy-to-use and creates nice charts and maps for embedding in websites. Created for journalists Must give email address to get embed code. No download. Many different chart types.
- RAWGraphs is an open source tool built on D3.js that lets anybody easily create a chart using a drag-and-drop system to identify axes and other chart elements. Many chart options. Allows download or embed.
- Chartbuilder does not have any advanced features, but is quick and mosly easy. It can only make line, column, or dot charts and you must paste in just the data you want in the chart. Allows export as .png, .svg, or .json