Laudanum

Seconded. The service is excellent, and the paid version for longer documents absolutely worth it.

Consulting, lecturing or writing on hire. Also, selling owned goods such as out-of-print books, clothes, electronics. Joined with this, drastically reducing expenses during these three weeks (no extra spending, switching to one meal a day, etc.)

Drawing. The simple ability to represent accurately anything is of incredible help in any situation where language is a barrier (either when not speaking it, or to explain something in a better or more visual way than language can). It is a very useful communication skill.