Packs are formed from males being cast out, and when they reach maturity they will attempt to take over another area, which means taking on the alpha males of those packs. By dominating, females will join their pack if they have a sufficient territory.
Also males will join packs but as subordinate animals, but it is all about fighting and territory.
Females will stay within the pack.
There is a great documentary about the wolves in yellowstone, i think it is called Black wolf or something
Domesticated dogs are actually considered to be one of the subspecies of Canis lupus, and their scientific name is Canis lupus familiaris. I think feral dogs are included within this subspecies. Dingos are another subspecies, Canis lupus dingo. You can read more about the classification of wolves and dogs here: http://en.wikipedia.org/wiki/Subspecies_of_Canis_lupus