Windows keyboards

Keyboard layout files and Input methods were available in Windows XP Pro for the following writing systems as of Dec. 28, 2006.

Latin--QWERTY, Dvorak, Left-hand Dvorak, Right-hand Dvorak
Arabic
Armenian
Bengali
Chinese Simplified
Chinese Traditional
Chinese Zhuyin (Bopomofo)
Cyrillic
Divehi
Georgian
Greek
Gujarati
Gurmukhi (Punjabi)
Hebrew
Hindi
Japanese Hiragana, Katakana, and Kanji
Kannada
Korean Hangeul and Hanja
Malayalam
Syriac
Tamil
Telugu
Thai

This list omits Mongolian traditional alphabet, Oriya, Lao, Sinhala, Burmese, Cambodian, Ethiopic, Cherokee, and Canadian Aboriginal Syllabics. All but traditional Mongolian are readily available for Linux.

Languages covered include

Afrikaans
Albanian
Arabic 
Armenian
Azeri
Basque
Belarusian
Bengali
Bulgarian
Catalan
Chinese
Farsi
Finnish
French
Macedonian
Galician
Georgian
German
Greek
Gujarati
Hebrew
Hindi
Hungarian
Icelandic
Indonesian
Italian
Japanese
Kannada
Kazakh
Konkani
Korean
Kyrgyz (Cyrillic)
Latvian
Lithuanian
Malay
Malayalam
Maltese
Maori
Marathi
Mongolian (Cyrillic)
Northen Sotho
Norwegian
Polish
Portuguese
Punjabi
Quechua
Romanian
Russian
Sami
Sanskrit
Serbian (Cyrillic, Latin)
Slovak
Slovenian
Spanish
Swahili
Swedish
Syriac
Tamil
Tatar
Telugu
Thai
Tswana
Turkish
Ukrainian
Urdu
Uzbek (Cyrillic and Latin)
Vietnamese
Welsh
Xhosa
Zulu