MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Clio - Clio provides a full suite of web-based practice management tools targeted specifically at the administrative needs of sole practitioners and small firms.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.
MyCase - Practice More, Manage Less.
Constant Contact - Constant Contact offers email marketing, social media marketing, online survey, event marketing, digital storefronts, and local deals tools.
PracticePanther - PracticePanther offers CRM, invoicing, time tracking and communication solutions for law firms.