I'm looking for some solid recommendations

I want to be able to collate (drag and drop) different lists into one address book that will automatically get rid of duplicates and ideally let me mail out to the whole address book in one go or to pre-defined groups within it

oh and if there is anything that will let me do all of this web-based (so that I can work from different machines/networks) so much the better

what dos the DiS office massive recommend?