See labrys, black triangle.
Bisexuals have historically been dismissed or distrusted both by the straight and by the gay community. For a long time, the prevalent attitude among homosexuals was that bisexuals did not exist, and were semi-closeted homosexuals.
That attitude has given way to a better understanding that some people are attracted to both men and women, to a greater or lesser degree. In any case, Bisexuality refers to desires and self-concept, not necessarily behavior.
Many bisexual people consider themselves to be part of the LGBT or Queer community.
See: hijra, berdache, two-spirit.
Other groups within the LGBT community
Other groups of sexual minorities which have formed significant communities and possibly cultures include the Deaf Queer community.
External link: http://www.deafqueer.org/
The polyamorous community is another sexual minority with an associated culture.
Another form of sexual minority that may form culture is that based around sexual fetishism. For example, practitioners of S&M and those who are into leather may have extensive cultural knowledge associated with their communities.
Influence on culture at large
Sexual minority cultures frequently and consistently influence the broader culture at large, including straight culture. Slang frequently originations in subcultures, including sexual minority subcultures, which becomes part of the larger vernacular including words associated with descriptions specific to sexual minorities or not. Madonna is one of many artists who have borrowed from sexual minority cultures, including her appropriation of vogueing. Recently, the television series Queer Eye for the Straight Guy depicts straight men being made over by gay men.