Ull (or Ullr or Uller) was the son of Thor's wife Sif (and Thor's stepson). His name means "Glory" and he was the god of archery, hunting, duelling, and skiing. He lived in Ydalir ("Yew Valley") and his weapon was a bow made from yew.

After Ull's soul mate Skadi (goddess of winter, hunting and skiing) left Njord, she married Ull. One can only assume that their marriage was happier than her first one...

Ull must have been a very popular deity in Scandinavia because of the frequency of his name in place names (e.g. Ulstein, "Ull's Rock").

Sources:
http://www.ugcs.caltech.edu/~cherryne/myth.cgi/Ull.html
http://www.pantheon.org/articles/u/ull.html