Here are the ones that already exist:
Arabic
Afrikaans (and Dutch)
Chinese
Czech
Danish
Dutch (and Afrikaans)
Esperanto
French
German
Hebrew
Hungarian
Indian (generic)
Irish
Italian
Japanese
Klingon
Korean
Latin
Lojban
North Germanic (generic)
Old English
Portuguese
Russian
Scots Gaelic
Spanish
Swedish
Toki Pona
Turkish
Urdu
Volapük
So, I'll start, I speak Hungarian, and studied Latin for 4.5 yrs though I've forgotten most of it not that I knew all that much to begin with

EDIT: I'll try and add people as they comment, as long as the rate of posts is low enough. This way if any language gets say 4 people, they can start a thread:
Code: Select all
Language -forum pop - speakers
Bahasa Indonesia-1 - Pit
Finnish - 1 - tendays, marleen
Greek - 1 - free eye
Hindi - 2 - aneeshm; tendays
Marathi - 1 - aneeshm
Norwegian - 1 - øsse
Polish - 1 - pfm
Serbo-Croat- 1 - Eugo
Tamil - 1 - tendays
Tagalog - 1 - Pit