The weekend Dark Horse sale is on 88 Sci-Fi books at $.99 each. Titles include some Aliens, BattleStar Galactica, Bionic Man, Deep Gravity, Ei8ht, Flash Gordon, John Carter, Predator, and Prometheus. Lots of Dynamite stuff, so be careful that you don't already own it on Comixology or one of the 63 Dynamite bundles.
https://digital.darkhorse.com/genre/222/
Marvel has a one-day sale on some highly rated recent series.
Peter David's All-New X-Factor (2014+) 1-20
Charles Soule's She-Hulk (2014+) 1-12
James Robinson's All-New Invaders (2014+) 1-15
https://www.comixology.com/All-New-M...Sale/page/6994
Some new collections have merged into the Marvel collections sale. Unknown duration, but advertised as limited.
https://www.comixology.com/Marvel-Co...Time/list/7116
From Jet City Comics, Symposium 1-3 are on sale at $.99 each, unknown duration. Anyone read this?
https://www.comixology.com/Symposium-Sale/list/7068
The ever repeating Fathom sale is back, ends 6/14/15, but I wouldn't worry too much about missing it. At least ten of the issues in there are free, fwiw.
https://www.comixology.com/Fathom-Sale/page/6996