The relationships, recently:

Archie & Betty & Veronica

Midge & Moose

Reggie & Harper

Dilton & Brigitte

Chuck & Nancy

Cheryl & the bald guy (George)

Kevin & Devon (though Kevin will grow up to marry Clay Walker)

Frankie & Maria

Ginger & Marcus

Jughead remains unattached, though Ethel Muggs has gone with him to more proms than any high schooler could ever be expected to attend. But “prom dates” is really a whole different category than “relationships”; in one of the first Veronica stories, “Prom Pranks” from Archie #1, Ms. Lodge is escorted to the dance by Jughead (who mistakenly gives her a poison ivy corsage).