What is the best way to manage a 300+ email distribution list/group?

You could analyze the possibility of using a CRM solution like Sugar.

Are you familiar with mail merge in MS Office? Create a data base with all the information you need and you can link it with a word document, you can also link excel files.

I would ask Kat what she uses for the newsletters. It seems to work just fine. Her Twitter is @KatArmstrong if you want to contact her there. She'll probably see your question anyway since she sent it out in the newsletter :P

I manage a list of around 65,000 for my boss. I use Mail List Controller and hMail Server. It works but can get rather pricey. It is cheaper in the long run to buy the software though. Otherwise, you can use constant contact or mail chimp.

I manage several lists for double opted-in newsletters. One of them is currently 72,000 recipients. I store them all in individual Access databases (mainly so I can program complex ways of managing them as is needed in their particular cases). I use a program called 'GroupMail5' to connect to these databases and send the emails. It is a particularly good program for this and the professional version costs less than $100 AUD (cant quite remember how much). It is distributed by Infacta. GroupMail5 then sends the emails to a Mailserver that I built myself, which is used only for sending these emails and receiving bounces.The Mail server has its own internet line. The Mailserver is Ubuntu 10.04 (Linux) with Postfix, virtual users and groups using Mysql, squirrelMail, spamassassin, Authd and some other stuff. There is an excellent step by step at "howtoforge" by a guy called FalkoT. The hardware cost less than $300 AUD brand new but will run on much older harware. I have setup reverse DNS and an SPF record with the DNS host. GroupMail5 also has an SMS facility. GroupMail5 only runs on Windows. This may sound like a long winded answer but the crux of it is, manage your list in a database - Access, MySQL,Base(OpenOffice) or similar. Connect to it with a Mailing software to send. There are many out there. Build your own MailServer using the helpful guys at HowtoForge. Give the mail server its own internet connection and line. I hope this has been of some help.

Most hosting companies have mail programs already built it. You have your database full of user info and then you just plug in what parts you want to generate for that particular mail. Click send and you're done.

Have a look at MailChimp.com It links to existing databases and allows selection of groups and control of email lists, generates mail shots etc.

If your lists are large and not 100% verified you can also use OfficialEmailMarketing.com