There's a nice page about the Hough transform (and some variants) here:

   http://homepages.inf.ed.ac.uk/rbf/HIPR2/hough.htm

Near the bottom of that page, under "Interactive Demo" there's a link to a
demonstration applet.  The source code used by the applet is available from the
same page.  From the look of the code, it is implemented more for simplicity
than for speed (doesn't pre-compute the sin/cos values for instance), but it
may be of some help.

   -- chris