We submitted our marketing site with a quick blurb to a handful of design blogs. We put a very brief and polite message and sent it around to a number of sites.
The responses were a little shaky, so we didn't know where it was going to go.
Next thing I know, I am standing in the Pabst Theater in Milwaukee, drinking a Blatz beer. I look down at my phone and see that Smashing Magazine (which had 1M+ followers at the time) tweeted our product and it took off like wild fire.