[pmorici]

That's about par for the course in my experience. You shouldn't wait around for these companies to get back to you, if you do that you'll never get a job. Apply to as many places as you are interested in.

My own anecdote; I'm already employed but am ready for a change and have been casually looking around to see if there is something interesting out there. At least twice I've done coding quizzes associated with a job posting and then been contacted to setup an phone interview time. Each time they setup a time and then don't actually keep the appointment. In one case they actually contacted me again several weeks later as if it was the first time they had emailed me. In both cases I believe the companies were small enough that the hiring was being handled by the "CEO" and there was no dedicated HR department. No way I would work for a company that does junk like that. Even if you do need to cancel an interview it's easy enough to send a 5 word email, "Sorry, I need to cancel"