What are your customer acquisition channels?

I'm curious what customer acquisition channels are actually working for you guys. A lot of the VC podcasts talk about scalable free channels but I suspect many of you are using PPC as long as you find that the users are converting.

I'm looking at long term SEO too but considering very targeted PPC in the short term.

Right now our only really successful channel is Hacker News and some SEO. Trying to improve on the SEO channels too.

#growth #customeracquisition