GRML 0.3 is the first distribution to ship mutt-ng. GRML is a live CD based on Knoppix and Debian, targeted at system administrators and text tool users. It's definitely worth a try, and I always have a copy of it with me with my work notebook (although that's still an older version w/o mutt-ng :-/). The lead developer of GRML,
Michael Prokop is also the one who contributed the wonderful
grml-muttng script that dramatically simplifies the creation of new mutt-ng configuration files especially for new users.