Funnel charts are, unsurprisingly, shaped like funnels. They are often used in sales to represent reducing numbers of prospects in a sales situation as the sales process moves forward (large numbers of unqualified prospects through to a smaller number of actual sales). Obviously they can be used for other purposes where several stages are involved with decreasing numbers involved in each stage.
Online funnel chart building tool.
Excel – A short tutorial on how to create funnel charts in Excel with a downloadable template.
PowerPoint – A free template for lead generation funnel chart.
RGraph – a free javaScript open source library.
jqPlot javaScript plugin to create funnel charts.
d3 javaScript funnel charts.