Hi!
On the pgAdmin3 site (http://www.pgadmin.org/pgadmin3/development.php#dev_snap) there's a link, pointing to daily snapshots for Windows. It is currently pointing to http://www.pgadmin.org/snapshots/windows which doesn't exist, it should be either http://www.pgadmin.org/snapshots/win32/ or http://www.pgadmin.org/snapshots/win32-installer/ .
--Lp,Miha