Ways of monetizing your list

Had a phone call from an internet colleague i.e. someone who I've been in contact with over the years. He was asking about buying an ad in my newsletter.

Stupid thing is I have no idea what this sort of deal is worth to him or me which is careless so I need to do some research. I also said that I had no idea as the cleanness of my list. In other words, how many names are complete junk.

Actually the system I use for emailing at the moment automatically deletes email addresses from my list if they fail to get delivered 3 times in a row which helps automate the cleaning process.

More work this a.m. on a new product idea plus a response by email to a request for some AdSense consulting. Will it come to anything? I've no idea!