Note: This time all the links go to Kobo, but I am sure that they are available at Kindle and BN as well. Except for With a bang, which is Kobo exclusive at moment.
Shadows by Jennifer Armentrout is free right now. This is a prequel novella, but I have heard that to avoid confusion, it is best to read book 1 Obsidian first. And Obsidian happens to be only 2.99 right noq.
Endurance by Ann Aguirre is 0.99 right now. This is a novella, and it is possible that this is the standard price.
Enclave by Ann Aguirre is 2.99 right now.
Shadow by Amanda Summer is free right now from Harlequin Teen.
The Babel Codex by Alex Archer is free right now. I liked the Annja Creed novels I read a couple of years ago ( Although the Scandinavian in me thinks her name should be spelled Anja.)
Not YA, but Maria E Schneider just released With a Bang, a dystopian Short Story that is free.
Oh, and Kobo have two 50% off codes right now, both expires at the end of Sept:
B2S50 ( single use)
Sept50 – expires end September ( Multiple Uses!!)