Hacker Newsletter - Best of Hacker News in your inbox every Friday.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Paperplane - High quality HTML to PDF conversion API for developers.
Brevo - Innovative online Email Marketing solution to manage your contacts, create & send your newsletters and track your results. More than 80 000 clients. Best prices and attractive features.
Why is this interesting? - Every weekday Noah Brier & Colin Nagy (and friends) send an email about something interesting.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.