Update:
I'm a huge fan of their (free) create-your-own flashcards, as
@DoReMiFaSo can attest. I think I've converted 75% of our pharmacology book to memorang sets at this point. I really like their USMLE products as well-- they don't cover EVERYTHING you need to know for boards, but it's a good overview of what's in First Aid, and it's a really useful way to cram those rote memorization details (looking at you, WBC cancer translocations) into your head. They just realized 2.0, and the format is much prettier than it used to be and it has some nice new features. Multiple "game" modes are coming soon, which is fun; the game mode they had previously is gone, and was my primary motivator for studying pharmacology after midnight.
I'm not sure if the paid subscription has a lot of utility for a first year, but since it's a lifetime subscription, you might as well buy it now if you think you might want it. I'm not sure but I think there's a discount right now because too the recent upgrade to 2.0. For clarification, I wouldn't say Memorang's competing with Firecracker-- it's more flashcards by subject than spaced repetition. It's more similar to the USMLERx fast facts (for the paid subscription) and Anki or Study Blue (for the free part).
Full disclosure: I'm a Memorang Advocate, but I don't get anything from them for posts like this or doing anything other than organizing discounts for my own classmates.