Freelancer Stack - Curated directory of tools used by 10,000+ freelancers
Bill.com - Bill.com provides ACH payments processing, automates your accounts payable and accounts receivable processes.
The Standard Freelance Contract - The first common standard service agreement
ChargeDesk - ChargeDesk offers billing support across most of the payment service providers.
Freelancelift - Community, training and support specifically for freelancers
Zoho Invoice - 100% free online invoicing software for small businesses.