When I was at SMX West 2010 in Santa Clara a couple of weeks ago, I attended a session called Technical SEO. One of the speakers was Maile Ohye (one of the best Google speakers in my opinion) who showed a very cool comparison of the various URL structures that can be used for multi-regional sites. Maile also discussed the advantages and disadvantages of using a country code top level domain (ccTLD = .ca, .co.uk, etc.) or a global top level domain (gTLD = .com, .net, .org, etc.) for multi-region websites.
Anyway, Maile mentioned the URL structure comparison chart from her presentation would be available online soon and here it is reposted in along with other great information by John Mueller. This should be very handy as a reminder for anyone planning their multi-region web marketing. Note that I quickly whipped up a slightly easier to read & print PDF version of the table shown in the article.
If you want more tips from SMX West I covered many with my co-host John Carcutt on my recap of SMX West on SEO 101 at WebmasterRadio.FM, March 15th, 2010.