I have been under a deluge of "return to sender" emails from
legitimate ISPs because my email address is in the 'reply to' line of
the spam.  My name is not used, but it is my email address, and
sometimes, a variation of the email address@mydomain, because my main
email address is the catchall account for my domain. Is there anyway
to stop this?  Spam is bad enough, but to now have my name (my email
address is as good as my name)  on spam emails going around the world
is infuriating.

My address was once used by a spammer to send out loads of junk mail. 
It was actually going out from my email, so I decided to change my
password.  That has prevented any further abuse of my addy.

If your email is the catch-all for the domain then you will need to be
sure the domain is locked to additional users and asking everyone in
the domain to change their passwords isn't a bad idea.

Those spammers are crafty and obnoxious.

Dianed,

*Everybody's* email address is being used in the Reply To line of
spam. When creating the email, you can set the Reply To to anything
you want, including somebody else's address. It's just yet another of
the crummy things that spammers do to make their junk emails the
problem of as many people as possible. Don't take it personally. You
haven't been singled out or anything. :)

- Hammer

I hope you pay this man, his answer is correct!

There's some good advice in this answer to an earlier question:

http://www.answers.google.com/answers/threadview?id=355995