Hmmm I'm a bit surprised that these sites charge at all for anything...cuz really I all want is the ability to maintain a list of email addresses automatically (subscribe, unsub, etc.). Are the services that these sites offer worth it for indie devs?
they're more than worth it. let's say you make commercial games, and release them pretty regularly; how else will you contact people interested in knowing about when your next game is released without an email list? you could ask everyone to subscribe to your rss feed or something, but that'll probably miss a lot of people who don't use rss. you need some way to keep in contact with your fans
you *could* email them individually yourself, but there's a couple of problems with that -- most email providers don't let you send to large numbers (hundreds or thousands) of people at once, they have a limit. they're also more likely to mark your email as spam if it was mass-emailed and doesn't have an 'unsubscribe' option on the bottom (they may mark it as spam anyway even with that, but the chance is less). plus handling all the subscriptions and unsubscriptions to your hand-made list manually is a lot of work
i'd say it's even a good idea for freeware developers to have a newsletter, because it'd be nice to be emailed whenever one of my favorite freeware indie devs releases a new game or a new update to their game
anyway, the one i use is YMLP "your mailing list provider"