Here's a round up of deaf organisation support:
European Union of the Deaf Youth
World Federation of the Deaf:
WFD expressed its support for the recognition of the Italian sign language
And their letter can be found here [PDF].
European Union of the Deaf
Letter from the EUD signed by 29 member countries
EUD letter. EUD President Berglind Stefansdottir & Board Member Humberto Insolera officially handed the EUD support letter signed by delegates from 29 EUD member countries to Sebastiano Manciagli, the board member of the Italian Association of the Deaf.
Austrian Deaf Association, Austria:
Letter to the Italian ambassador
British Deaf Association, United Kingdom:
BDA supports recognition of Italian Sign Language (LIS)
The Canadian Association of the Deaf (CAD) strongly supports the recognition of the Italian Sign Language.
Irish Deaf Society, Ireland:
Press Release from the Irish Deaf Society: Vigil at the Italian Embassy, Dublin
German Deaf Association (Deutscher Gehoerlosen-Bund e.V. or DGB)
National Association of the Deaf, USA
NAD supports recognition of Italian Sign Language (LIS)
Did I miss an organisation out? Let me know - I will add them. Your national deaf organisation not on this list? Nag them, and ask them to put it online. Ultimately this is an international issue, and Italy has asked the world for support.