We've got quite a large site (500k indexed pages, much of it user-generated content) but have new company-created content that is country-specific to half a dozen different countries.

As we add more country-specific content (half of it dynamically generated data), I'm wondering if I should create a series of micros-sites for each specific country, or continue adding the content to my main domain.

Two additional questions:

1) Should I add foreign language for each specific country as well as English? Has anyone ever done this and seen country-specific SEO boosts?

2) Should I link them back to my main site somehow, or should I keep them as separate entities specific to each country and manage multiple SEO campaigns? We get over half our traffic from long tail organic, and am wondering if we can do that for a half a dozen other domains that are country-specific and full of useful, compelling data we offer for free.