[exim] Virtual Host Help

Can anyone direct me to some decent documentation or instructions on how
to setup virtual hosting with EXIM? We have been doing things manually
for a long time, and probably not the correct way (in other words I have
a mess on my hands). I could also really use a pointer to a "control
panel" type of software where basic admin stuff for domains being hosted
on our machines can be left for the domain admin.

Any help that those who have done this before can provide would be
GREATLY appreciated!

Thanks,
-Chris