The Mary Sue is currently posting an ongoing series on the history of LGBT portrayals in comics:

Next month is June, aka LGBT Pride Month. In anticipation of this, and because it is good and necessary to discuss representation in pop culture and media, we present to you this look at how LGBT content has been portrayed in mainstream American comic books. This is by no means a complete history. We don’t have the space for that. But we hope you’ll appreciate this look at some of the major forces that have shaped stories and characters in the mainstream comic book medium.

Read part 1.
Read part 2.