For the Long Version, I like to use the gingerbread person:
So, I explain that while I am female and express femininity, I am attracted to those who express as masculine, but who are chromosonally XX, be they FTM, TG, or butch women, which makes me queer and often at odds with the popular lesbian community.
The 5-second version usually involves the phrase "my ex-wife" [was the same way, did the same thing, took all my money] LOL It's relatively clear.
I rarely utter the words "I am a lesbian". Straight people don't say "I'm straight". They just talk about their life like it's completely normal, even if I think they're weird. ("My boyfriend loves fireworks and builds rockets.") So, I follow their lead and do the same thing. ("Your boyfriend likes blowing stuff up too? The woman I'm dating helped design the cruise missile system. One of our favorite vacation spots is near a blast site.")
I used to "come out" in those terms, "I'm gay". But it opens people up for a political conversation I don't always care to have. Approaching it the other way does not leave them any room to attack. It says, "we are not different" rather than "I am different from you in this way" It does not have an agenda, except to seek common ground.
Even the most conservative people have a hard time labeling you as some radical dyke if you approach things in this way. You're talking about your life, I'm talking about mine. We're just two people wandering through the world. If they are that averse to gays, they'll politely end the conversation and stop telling me about their gross hairy boyfriend in the future. It's a win-win.