Thanks to everybody who participated, you are terrific! I'm sorry for not answering right back.
Since most answers are screened, I'll give an impresonalized summary here under the cut (see below), Maybe later I'll contact some of the commenters via presonal messages.
Further comments are welcome.
"For a project of mine I'd like to ask everybody to put here new (or reused old terms) that are used instead of more traditional as "husband". "wife", "girlfriend". "boyfriend"...
All terms referring to any couples and romance, regardless of sexual orientation and social norms are welcome. Any language will do (but please explain the meaning of the term and tell me by whom it is used)".
AND HERE ARE MY FINDINGS. I personally love the idea of "it's complicated" as a noun :^)))
"Partner" and "Significant Other (SO)" are both used widely. But some object to "partner" as "too clinical" ("it's a relationship, not a business contract"). SO may be used to accentuate that it's a same-sex relationship.
There seems to be a bit of controversy regarding the use of traditional terms "wife" and "husband" versus "partner" in a same-sex marriage\civil union context. Same-sex couples may use traditional terms to accentuate the legal "normalness" of their marriage, yet other such couples may reject the traditional terms and even be offended by these.
Boyfriend\girlfriend may be thought as "too juvenile" and substituted by oldstyle expressions like "gentleman friend"\ "man friend"\ "lady friend" and the like, also by "partner" or SO
And here are some more juicy words
"spice" - plural of spouse among the polyamorous. This comminity has its own rich lexicon.
Rural Australia: "old man" or "old fella" or "the old bloke" and "old lady" instead of husband and wife
"Friend with Benefits and More" (opposed to just "Friend With Benefits") - sort of a border situation where casual sex without strings may evolve into smth more
"it's complicated" jokingly used as a noun - comes from Facebook profiles
"mate" - as in "mate for life", also used by the furry community because of the animal connotation
"boo" (boyfriend\girlfriend) sometimes assosiated with Afro-Caribean language (some say "boo" is a term that is derived from the French word "beau", dunno if it's the real etimology).
Philippines: a informant says "mommy" and "daddy" are common there