The best way you haven’t mentioned is getting natural inbound links. That’s the absolute best, and the absolute hardest.
Honestly, my content hasn’t been able to get the “sticky” factor so the readers keep coming back, let alone link to my site.
How about a viral marketing ploy?
I heard of someone coming up with an ebook, and then making a .pdf of it and placing it on bitorrent. Does it work? I have no idea, but it’s worth a try.