We have a few new localization teams putting a whole lot of effort in getting their languages up and running. For those, the l10n server is creating language packs right now, and as always, they can use as many eyes as possible.
The right welcome for Runa, Rajesh and Timothy is a Mozilla welcome, so pound their work and file some bugs ;-). If you know someone speaking Bengali, Hindi, or Ukrainian or happen to do so yourself, you want to download their language packs, set browser.useragent.locale to bn-IN, hi-IN, or uk resp. and restart.
The best way to provide feedback for those can be found on the respective team pages.
Update: Filmil fixed the Serbian language pack now, too. Woot.