Dygraphs is an open source JavaScript library that you can use to create interactive, zoomable charts of time series, capable of displaying huge data sets and enabling users to explore and analyse them. Check out the examples at the link, along with sample code to get you started. Looks dead simple to use. Dygraphs sends no data to any servers – it is client-side JavaScript, processed entirely in the client’s browser.  If you work with JavaScript you’re going to love this because as far as I can see it really transforms the user interface potential of the language into something terrific.