If you are looking to help with translation of the Arduino IDE, please use Transifex :

From version 1.01 of Arduino's IDE, you will be able of choosing your preferred language. For that to happen we need your help in translating a text file that contains all the different strings in the IDE: from menu names to error messages.

Some of the currently supported languages include:

How manyLanguageas it iscodestatus
1Arabicالعربيةardone by Belal Affouri and Ameen Sarsour
2AragoneseAragonésandone by Juan Pablo Martínez Cortés
3CatalanCatalàcadone by Albert Segura
4Chinese台灣正體zh_twdone by Yehnan
5Chinese Simplified大陆简体zh_cndone by Ledong
6DanishDanskdadone by Anders Bech Mellson
7DutchNederlandsnldone by jo3ri et al.
8EstonianEestietdone by Cougar
10FrenchFrançaisfrdone by carignanboy1 (Canadian)
11FilipinoPilipinotldone by Marc Lester Tan
12GalicianGalegogldone by Diego Prado
13GermanDeutschdedone by Lukas Bestle and Benjamin Hogl
14Greekελληνικάeldone by Vasilis Georgitzikis
15Hebrewעבריתhein progress
16Hindiहिन्दीhiin progress
17HungarianMagyarhudone by Robert Cseh
18IndonesianBahasa Indonesiaiddone by Rininta Andari
19ItalianItalianoitdone by Sara Gallo and Simone Majocchi
20Japanese日本語jadone by Shigeru Kanemoto
21Korean한국어kodone by Jinbuhm Kim
22LatvianLatviešu Valodalvdone by Kristofers
23LithuanianLietuvių Kalbaltdone by Laimutis Palivonas
24Marathiमराठीmrdone by Sarvesh S. Karkhanis
25Macedonianмакедонски јазикmkin progress
26Nepaliनेपालीnein progress
27NorwegianNorsknodone by Rune Fauske
28Persianفارسیfadone by Ebrahim Byagowi
29PolishJęzyk Polskipldone by Maciej and Maciej Wójciga
30Portuguese (Brazil)Portuguêspt_brdone by robmachado et al
31Portuguese (Portugal)Portuguêspt_ptdone by Nigel Randsley
32RomanianLimba Românărodone by Pop Gheorghe
33Russianрусский языкrudone by Stanislav and Evgeniy
34SloveneSlovenski Jezikslin progress
35SpanishEspañolesdone by Juan Gomez et al
36SwedishSvenskasvin progress
37Tamilதமிழ்tadone by Ram Kumar Y
38TurkishTürkçetrin progress

When a language is listed as in process, you can still collaborate, please check the email list and join the translation work.

If you feel like you have an hour and that want to contribute, subscribe to the translations email list at this page. Also visit Transifex : . You can see a complete list of translations and those in progress.