If you are interested in to learn about, solve your problems with and/or contribute to multilingual Drupal, DrupalCon Barcelona is the place to be. Here is a quick summary of things happening so you don't miss what is going on.

1. Extended sprints before and after DrupalCon (19-21 and 26-27 September) are happening, and the multilingual team is there.
2. Lingotek is holding a free training on Monday 1-5pm to translate Drupal sites with all the benefits of the lingotek module and services. Also a BoF on the same topic on Thu 10:45 to 11:45am
3. Intersted in localize.drupal.org and translating Drupal itself? Come to and discuss at Bring Drupal 8 to all in their native languages on Monday 11am to noon.
4. If you'd rather see the real life experience of Acronis, there is also a BoF presentation at the same time (Monday 11am to noon) titled Drupal 7 - Internationalisation for custom enterprise environment
5. Drupal 8 comes with a whole new set of multilingual features, which combined with other improvements is even more powerful. Drupal 8 multilingual site building hacks is the place to be to see that in action.
6. Just want your problems solved and move on? The multilingual therapy BoF is on for that on Wednesday lunchtime. Bring your lunch and questions/problems.
7. If you don't have time or the opportunity to come to the Drupal 8 site building session, get the executive summary at the Acquia booth at 3:15-3:45pm on Wednesday (in the break).
8. Tired of all this multilingual stuff? Want to learn how we managed to be so active for four years on so you can get your movement going better too? Your place is at Open source project management in the Drupal community, lessons from the multilingual team Thursday 1pm to 2pm.
9. Just want to get stuff done (fix UI text, solve bugs, figure out issues) in core so you don't need to solve them over and over for your customers? We are also at the sprints on Friday and the community is even offering plenty of mentoring if you are entirely new. No excuses to not contribute!
10. While not primarily multilingual content, there is also multilingual coverage in Entity storage, the Drupal 8 way, in Our experience with building Drupal 8 Sites in Alpha and Beta, in Configuration management in Drupal 8, in Building sites in Drupal 7 with an eye on Drupal 8, as well as in Let's build it on Drupal 8 and some others I likely missed (sorry for that).

Hope to see you at some of these places!