<p>Is there a <a href="http://en.wikipedia.org/wiki/Box_plot" rel="nofollow noreferrer">Box Plot</a> 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?</p>

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.