as salaamu alaykum,
Madina Muslim Community
Madina Forum - A City of Muslims
is also nice but might seem like its only for Muslims.
Personally I like 'The' Madina instead of just Madina. It sounds cooler
The Madina: An Online City for and About Islam & Muslims
I think you should also play off Jannah.org (The garden)
ie the Garden & the City
In the intro paragraph you can put something like this is the city that grew from the garden, since the madina grew out of jannah.org!