[Proj] Help translating NAD83 coordinates to WGS84

[Michael Frumin]

I'm having trouble converting some US coordinates from NAD83 to WGS84.
These coords were generated by geocoding addresses with US Census
TIGER/Line data but I'm trying to map them onto maps generated using
WGS84 (Microsoft Mappoint maps, which use NavTech (?) data).

As is, I've been reading
http://www.remotesensing.org/proj/gen_parms.html and tried using the
cs2cs utility from proj, but to no avail - no transform is actually
applied:

cs2cs -rs -f "%.10f" +proj=latlong +datum=NAD83 +to +proj=latlong
+datum=NAD83 
40.76471        -73.97813
40.7647100000   -73.9781300000 0.0000000000

there are plenty examples of using cs2cs with the +ellps parameter, but
I don't know what ellipses are in use.  Any thoughts there?

Also, I've seen the documentation for the +towgs option but I think it's
pretty much over my head.

Any help would be awesome - it's for a cool new feature on
http://www.fundrace.org

Thanks,
Mike Frumin
mfrumin at eyebeam.org