All Mozilla L10n projects are volunteer efforts by relatively small groups of people or single persons,
official teams are listed at MLP pages, not all of them provide current builds though.
114 teams, Mozilla 1.7.5: 21, 1.7.3: 33 languages
30 (57) teams, Firefox 1.0: 28 languages (40 planned for 1.0.1/1.0.2)
49 teams, Thunderbird 1.0: 23 languages
- Camino, Sunbird, Nvu have ongoing efforts, but aren't yet on MLP pages (that is planned though)
(All language counts are without en-US)