After mapping race courses, the next logical step seemed to be visualizing the races themselves, similar to BBC Tour coverage (link thanks to Russ) and at least one overseas marathon I've seen online (but can't remember which).
This 10k race demo shows how it could work, using Microsoft Silverlight beta 1.0 and Microsoft Expression Blend.
Got some other Silverlight ideas... stay tuned.
EDIT: Now calculates km markers automatically, and shows altitude as well. Now it really needs to support split times rather than race-average (so the 'runners' slow down on the hills!)
EDIT2: Although some 'matrix glitches' are present, km splits are now supported. Watch red catch green in the 2nd lap! The 'jumping' is due to a bug when a line segment is "split" to accomodate an intra-segement marker... kinda know where it is but too late (at night) to fix it now...