Is there a Box Plot graph, or box and whisker graph available for Reporting Services 2005? From the looks of the documentation there doesn't seem to be one out of the box; so I am wondering if there is a third party that has the graph, or a way to build my own?
There definitely isn't a Box Plot built into SSRS 2005, though it's possible that 2008 has one. SSRS 2005 does have a robust extension model. If you can implement a chart in System.Drawing/GDI+, you can make it into a custom report item for SSRS.
There are a few third-party vendors with fairly feature-rich products, but the only one I've ever evaluated was Dundas Chart, which isn't cheap, but gives you about 100x more charting capability than SSRS 2005 built in (for SSRS 2008, Microsoft incorporated a great deal of Dundas's charting technology). I can't say from experience that I know Dundas Chart supports the Box Plot, but this support forum post says so.
We implement a box-plot with Dundas Chart for Reporting Services 2005.
Unlike the default chart tool, Dundas allows you to chart multiple values using different chart types on the one chart.
This means that you can create complex graph types by adding different chart types. E.g. you can plot a line, and a floating column chart.