Back in October, I gave a talk at Drupal Camp Montreal called Tips & Tricks for Building a Multilingual Site with Drupal. It was a great opportunity to review the multilingual features that we use on a day-to-day basis.
The quality of the i18n module has greatly improved in 2009, and modules like menu translation are now stable. There are a few modules like ubercart and organic groups which have issues when internationalization is introduced, and so I discussed some work-arounds that we've used.
The video of the talk is now available, thanks to DBN's hard-working videographers. You can also download the slides from the Drupal Camp website.