Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Clio - Clio provides a full suite of web-based practice management tools targeted specifically at the administrative needs of sole practitioners and small firms.
7todos - A task board for indie hackers
MyCase - Practice More, Manage Less.
TaskPaper - Plain text to-do lists for Mac
PracticePanther - PracticePanther offers CRM, invoicing, time tracking and communication solutions for law firms.