We have all this awesome i18n functionality baked into 2.2, but never really got around to making languages switchable for website users :)
as we're pretty busy polishing existing functionality, it would be awesome if somebody could help out here:
http://open.silverstripe.com/ticket/1889
it is a good opportunity to get an insight into the internals of the i18n-behaviour, and an easy start into widget-development. anybody keen?