How to Handle large Distribution lists

I need to create multiple distribution lists for emailing to groups of
clients. I want to have some employees type the names into something that I
can import to an individual address book seperate from my personal one. From
there I was going to create a distribution list.

What is the best approach to this? Is there some way to use Excel or Access
to create these lists and then import them somehow. Is there a way to
directly create a distribution list without the addresses being in an address
book? We are not on a network so any network approach to this is not
applicable.