the only calligraphy course I know of is at Portland State University, and it's a summer course that covers the history of calligraphy, reading the various styles, and writing ruq'a. To get something written well, you'd be better off finding a local artist- ask around at a mosque, etc- most people will know of someone who does wedding invitations, etc. using the internet is really hard because it's difficult to convey what kind of shape, style, etc. you want. there are books to learn arabic calligraphy (i have one on ruq'a) but it takes a LOT of practice and the books can be expensive.