ChargeBee, a startup for billing for startups :)

Subscription Billing | Recurring Billing | SaaS Billing | Online web apps | ChargeBee

http://www.chargebee.com/about.html

Billing as a consultant - good thread on HN

Quit My Job For Consulting: Two Months Later | Hacker News

Consultants have a lot of implicit costs (that employees don't) which they should take into account when deciding what rate to quote.