My photography forum used to be pretty busy, but it's going to be replaced by a custom site... when I get round to it.
The funny thing is I thought running a photography community would be fairly easy, but it proved to be the most challenging - it's very difficult for people to take (and sometimes give) criticism of work.
I would just google photography forum and read a few - the culture will be quite different on them, some will be more welcoming of newbies than others..