A few people have suggested in different answers and on a couple of different blog posts I've read recently that it is a good idea to put your beta site on Hacker News, for example:
If you have a product in beta, post something on HackerNews to let them test it out before anyone else. They love that.
I've already had a look around HN a few times and I'm not sure where on the site I should be doing this. I don't want to tread on any toes and want to make sure I get it right the first time, can someone provide me information on the right approach for doing this?