Following on from the translator theme, Georgia Katsarou has done a huge amount of work on the Greek translation of Koha. As well as that, she has spent lots of time on translating the Koha manual into Greek. If that wasn’t enough she also runs http://kohaprojectgr.greeklis.org/ which is a very valuable resource for people seeking more information about Koha.
I bet for a lot of you, she really is unsung, but she is definitely a hero (heroine?). I know I’ve said this again and again, but it is the people around Koha, not the software (although that’s pretty good too), that make it a great project to work on.