iTunes Switzerland, Denmark, Sweden and Norway [and Australia] [Updatedx2]
Music.ch claims (German) that Apple will be launching the iTunes Music Store for Switzerland as well as Denmark, Sweden and Norway on April 28th (Thursday).
This information is reportedly based on an internal memo.
Unclear is how much pricing per song will be for the individual countries.
Update: iTunes Australia is also expected to be released on April 28th according to Russell Crowe:
[Russell Crowe] said the local iTunes Music Store would become available on April 28, just a day before the launch of Apple's new operating system Tiger X
Earlier rumors had placed the launch in late April.
Update: Apple's servers are already hosting country specific images for the new iTunes Stores: