DreamHost makes phpMyAdmin available to you, which makes it very easy to add, edit, and delete tables, fields, and records. It also allows you to export your data in various different ways.
I'm afraid I'm not familiar with formmail, since I always write my own things to do this; however, if you have a basic knowledge of PHP, it is actually quite easy to do. Validating email addresses is not a difficult task to do, but it is easy for someone to give you a perfectly valid, but totally bogus address. Emailing them a link to the download page certainly gets around that problem. PHP can easily handle the email aspect as well.
Keystone Websites | si-blog