I put out a call for blog prompts on facebook and had this suggestion: "If you could have any piece of classic literature but with explicitly canon queer character, which would you pick?"
The thing about asking this question of an author is that it isn't exactly rhetorical. You can be sure that if we have a favorite story that needs queering, we've contemplated making it so (and may even have it on the writing schedule). And with the current acceptability of classics/genre-crossovers, such projects don't need to be confined to "just for fun to circulate among friends." But I suspect the "classics" that come to my mind may be a little more obscure than most. Here are some stories that I've run across in my research and reading that I either have or plan to write my own versions of that turn faint suggestions of queerness into main-text.
The Romance of Silence - A lesser-known work in the Arthurian mythos, involving a girl raised as a boy who becomes a famed knight but gets in hot water when the queen tries to seduce "him". I've actually written a short story heavily adapted from one of the episodes in this story, with Silence coming to terms with non-binary identity in the midst of peril and adventure. The story has been collecting rejections for the last couple years and I'm running out of places it seems logical to submit it.
L'Escoufle - Another lesser-known medieval romance that is part of one of the French genealogical cycles. I like that the implied romantic connections between women arise out of women's spaces, rather than being enabled by cross-dressing and gender confusion. It is, in essence, a quest adventure with a female protagonist. I have solid plans to write a medieval fantasy based on this, but have a lot of background work to do first.
The Travels and Adventures of Mademoiselle de Richelieu - This 18th century picaresque novel (well, it's a bit more complex in genre than that) needs almost nothing except a little character self-awareness to bring out the love story between the two protagonists, who go romping across Europe together disguised as men and are constantly teasing each other about how, "If I were really a man, then I'l marry you and we'd live happily ever after." And then--at the end of the adventures--they settle down together and live happily ever after. The story doesn't need much at all to make it queer (they just need to stop with the no-homo thing all the time!) but it does need some drastic editing to make it readable for modern tastes. My plans for it are a bit more complicated than that, involving a sort of modern/historic crossover...well, let's not give too much away.
Yde and Olive - This may be the best-known and most widely adapted medieval same-sex marriage story. It's one of the several medieval romances where a cross-dressing woman gains recognition as a knight and ends up in romantic entanglements with a woman as a result. The fact that there are several variants of the story make it ripe for further adaptation.
There are also a number of older works of literature that I have plans to extract bits and pieces of, but not re-write the original story itself. (Hervor's Saga lends a significant chunk of inspiration to a Viking-era story that I've had sketched out for a couple decades.) So, not "classics" in the sense of widely-read best-sellers, perhaps. But they're all stories that, to me, call out to turn subtext into main-text and turn the queer themes from covert hints into overt plot.