I call my wife my partner. It's what I've called her for years before we actually got married, and it applies to our relationship better than anything else I can think of. She's taken to calling me her wife more often, though.
As for our significant others, we tend to refer to them as housemates to people who don't know about our relationship. To people who do, they're our boyfriend and girlfriend.
I'm a 26 year old bisexual woman married to a 31 year old bisexual woman and we have a live in boyfriend and three girlfriends.