We've seen one archangel, and I believe there's a reference to another in the books.
Traditionally, there are seven archangels (Book of Enoch and Book of Esdras). The names vary from tradition to tradition, though the first four of pretty consistent. Ones I can remember are Michael (warrior, guardian of the south and element of fire), Gabriel (messenger, guardian of the west and element of water), Raphael (healer, guardian of the east and element of air), Uriel (watcher, guardian of the north and element of earth), Remiel, Salathiel, Azrael (Angel of Death)