US and UK versions of content - how do I get spiders to index both?

Detecting browser language settings and coping with search engines

[philicious]

I asked a question here [webmasterworld.com] about detecting languages settings (eg en-us, en-uk, en-nz) and delivering custom content accordingly, but my big concern now is with the search engines.

we have two sites that are targeting keywords that are spelt differently in English and American ("xxxx customisation" vs"xxxx cusomization"). We would like:
a) For our website visitors to read the version of the site that fits their browser settings
b) Search engine robots to index both sets of content.

Any recommendations on how this can be done?

[engine]

This might sound daft but, can you have an entry page with a USA flag and a UK flag so that visitors can click on one or the other, depending upon their location?