There are two teams who observe very distant supernovas to measure the geometry and expansion of the universe:

Supernova Cosmology Project (Lawrence Berkeley Lab):

http://www-supernova.lbl.gov/

High-Redshift Supernova Search:

http://cfa-www.harvard.edu/cfa/oir/Research/supernova/HighZ.html

News story on the recent results on supernovae in cosmology:

New York Times, Tue Mar 3, Science Times, p.B11 (Natl Edition).

For other activities of Kirshner's Harvard/Smithsonian supernova group, see:

Supernova News - Home Page

http://www.cfa.harvard.edu/supernova/