Ask HN: How would you promote a social network start-up?

Hello all!

My bosses have just bought a social network website with 20K+ userbase and 80K pageviews per day, it is basically a copycat of facebook for Russian market. We have large social networking websites here in Russia like vkontakte.ru, odnoklassniki.ru with tens of millions of users, so the competition is quite high. Our goal is quite ambitious – to get a decent market share and grow our audience at least to 1M users in the first year. The problem is that our marketing budgets are relatively small and absolutely not comparable to those big players.

Ideas that have come to my mind are referral contests like "get more friend signed up and win an iphone", cross-promotion with our friendly websites, sending invitation to users from email accounts, maybe some kind of viral videoclips...

Any more ideas how to promote a website like this?

P.S: I don't have any realworld marketing experience, I'm actually the CTO of the project but would like to contribute to project success as well.