SlimPlanner - Team scheduling, resource planning, task management
Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Hub Planner - Transparent Resource Scheduling, Timesheets, Vacation, Resource Requesting, Project Management & powerful Reports in an agile designed, feasible & intuitive software for simple planning
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Free Invoice Generator - A free invoice generator for startups
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.