According to this story in People magazine, a new album is due to be released in May by two of the three Dixie Chicks.
Lead singer Natalie Maines sat out as sisters Emily Robison and Martie Maguire recorded an album as Court Yard Hounds. On May 4th they’re releasing an album of the same name, and that link to the People article will take you to where you can hear a sample song, the single “I Miss You.”
The official site of Court Yard Hounds (with streaming audio) is here, and YouTube videos explaining the duet are here. Oh, and their MySpace page is here.