A selection of major publishers accepting unsolicited manuscripts*:
HarperCollins (US), digital first Harper Avon (romance) and HarperLegend
Harper Impulse (digital-first romance imprint of HarperCollins)
Hachette Australia: general email subs
Allen & Unwin, Friday Pitch (any day!)
Pan Macmillan, Manuscript Monday (first Monday of every month)
Random House Australia (accepts hard copy only for adult titles; email only and Feb-Nov at Penguin Random house for children’s)
Penguin Australia, first week of each month, email only: Penguin
Escape: digital imprint of Harlequin Australia, www.escapepublishing.com.au
Carina Press: Harlequin digital-first single-title imprint, includes novellas and short stories
Bloomsbury Spark, digital imprint (teen, YA, new adult, 25-60k words)
Jo Fletcher Books (Quercus speculative fiction imprint)
And agency Curtis Brown is open to unsolicited online submissions: check out the Curtis Brown guidelines here.
Google is your friend, but subscribing to free e-newsletters from writers’ centres will also provide current opportunities (members will usually get access to more).
Also see searchable Duo.trope (pay wall)
For speculative fiction markets and contests: ralan.com
Familiarise yourself with competitions offering publication (see state literary awards and contests such as GriffithREVIEW‘s novella project and Seizure’s Viva la Novella contest) [always check conditions of entry when entering any contest, especially for which rights might be claimed by the publisher]
* Read guidelines carefully. I know nothing more about these programs than what’s on the websites.
Updated 6 Mar 2018