Getting users 
sachinag: Honestly, the number of your users is directly correlated to your potential market.  Patrick's bingo cards are going after a much smaller market (teachers) than Drew's online storage (everyone).  Colin's online storage for technically astute paranoids is probably somewhere in the middle.So it really doesn't matter what you do if you're not targeting your market correctly.  You have to be honest with yourself and figure that out first.  Blogging on your blog isn't as good as being a good member of the relevant messageboard for your particular community, for example.  (At least not for your first 1,000 users.)For us, it was cold calling on the seller side and PR on the buyer side.  Turns out that the tech blogs have been much more willing to write about us than the gaming blogs.  I don't get that, but hey, whatever.  YMMV depending on your initial vertical.