Zoo City (which is also $1.99 on Amazon),
vN,
Blackbirds (which has dropped further, to $1.39), and
Embedded ($1.39 too) are all published by Angry Robot Books. Several of their other titles are also bargain-priced at the moment. Links to Amazon, but I imagine they've gone down most places:
For $1.39:
Empire State by Adam Christopher
The Hammer and the Blade by Paul S. Kemp
The Alchemist of Souls by Anne Lyle
$1.99:
Nexus by Ramez Naam
The Lives of Tao by Wesley Chu
Three by Jay Posey
Some of these are repeat bargains, but others have never been discounted before.