SEO for multilingual sites: language-specific results without changing URL?

Question

I have a site that has 2 languages: English and Swedish.

What I want is, if someone Googles the site in Sweden, it should show the Swedish results. That is, I want Goo

Answer 1

UPDATE IN 2015:

Google now supports Crawling and indexing of locale-adaptive pages!

Cited from the linked post, they support:

...

• Geo-distributed crawling where Googlebot would start to use IP addresses that appear to be coming from outside the USA, in addition to the current IP addresses that appear to be from the USA that Googlebot currently uses.
• Language-dependent crawling where Googlebot would start to crawl with an Accept-Language HTTP header in the request.

...

Although they still recommend using separate URLs.