You want to see a busy mailing list?
Just check here: http://lists.gnu.org/archive/html/qemu-devel/2008-11/threads.html
I was looking to see when qemu,
a very cool virtual machine for many hosts and many target CPU
architectures, was going to come out with a new release. As part of
that, I was checking to see if it was under active development. Well,
with 55 e-mails on November 13'th when I looked, I guess it is :).