I have someone who would like me to set-up a newsletter for their site. What script or software would be best? I need it to have double opt-in and be able to send html messages.
Definitely worth it. Use a sevice like aweber.com, there are several out there. Then you won't have to worry about bulk mail sending limits from your host or spam complaints from your recipients.
I've written my own scripts in both PHP and ASP and never had any problems with either. Just add the e-mail addresses to a database, then run a loop that goes through the db and sends out e-mails to each address.
I could see it being an issue with your ISP though, and if you're worried by that... i could see how a service could be worth it.
I'll have to talk to the person that I am doing this for and see is they are willing to pay for a subscription service. Thanks for the suggestions. I'll pass along the info and see how it goes.