Gradual engagement
For instance, Yahoo! uses this tip on the homepage. When you click on "More Yahoo! Services", you will see a menu coming from the left part of the page, with new options.
As I find this method particularly efficient, I decided to use it on my own site for english-speaking users. When you click "Don't speak french" on the top-right corner, you will see a block coming down to show you what content is available in english.
This is a tricky way to be sure that english-speaking visitors are not going to run away from my site because it's in french :)


