Victorian Lit: all those unread novels by Dickens, Eliot, Gaskell, Collins, Hardy... I could go on, but you get the idea. No matter how many I've already read, there are always more to tempt me. And then there are all the biographies of the Victorians. Sigh. (This is a popular area, tempting Dorothy and Danielle as well) And along with these I would really like to read up into the Edwardian age.
Science Books: I do try to read a regular rotation of science books, though I never seem to get to them frequently enough. Joining the Science Book Challenge has given me a bit of a push, and I've discovered a few really good reads. But of course now that I see other people's reading I have a longer TBR than ever
Virago, Persephone, NYRB: these publishers can never go wrong. I love their books.
Random Classics: as Dorothy said, there are all those classics that you've somehow missed out on reading. For me, that would be largely the Russians, but also some of the French writers, and of course, random novels from elsewhere.
Poetry: I enjoy poetry and go on a bit of a reading rampage every April, but I'd like to be a little more systematic and read all year round, plus study some of the lit crit around some of the poets I don't know too much about
Letters and Diaries: Stefanie mentioned this category, and it reminded me that I used to read this kind of thing quite extensively. I haven't for a while...why? I love them! I have quite a number of collections of letters and a few literary diaries that are now calling to me from their dusty homes on the shelf.
Mid-century women's fiction: I have a strange fascination with little known women who were popular enough at one time but are largely forgotten or considered pretty much non-literary these days -- Elizabeth Goudge, Rumer Godden, and those types of writers.
Works in Translation: I could always use more time to fit more translated works in. There are just so very many I want to read, and I am always finding more. It would be nice to wallow in the literature of one country for a while and then move on to another, and another...
Ukrainian history and literature (esp. Canadian-Ukrainian works): this area should be self-evident. I want to read more about my family heritage, and explore how others write fiction about their experiences as immigrants or first/second generation Canadian Ukrainians.
Re-readings: I never feel like I have time to reread all the things I'd love to. There is always something new calling out to be read! I have spent most of my reading time lately reading contemporary fiction, but would love to revisit some childhood classics, and for some reason I am really itching to reread Woolf, and maybe Proust as well.
How about you? Are there whole whacks of literature that you'd love to dive into if your time was utterly unlimited and you could read to your heart's content? Have you already made a list like this that I have missed?