The Enterprise Web 2.0 revolution has been a godsend to small and midsized companies. Inexpensive, web-based tools and services mean the little guys now have access to professional office tools that rival those used by the Fortune 500–at a fraction of the cost. Think Thinkfree, Zoho, Google Apps, and literally hundreds of other web office purveyors whose innovation and effort has made the web a more effective and friendly place for business transactions for small businesses, entrepreneurs, and their customers.

FreshBooks, provider of a popular online invoicing and time-tracking service now used by more than 180,000 business users, wants to make the web even friendlier. The four-year-old Toronto-based firm today released its API and opened the door for application designers, businesses, services companies, and users to integrate the FreshBooks’ billing platform into what it hopes will be an entirely new category of products, features, and solutions for enhancing and streamlining productivity, workflow, sales, CRM, project management, and invoicing.

Application/service integrators can incorporate FreshBooks APIs into existing and new products to extend functionality, including timers, project planners, and desktop widgets. Services providers, such as ISPs, Web apps, wine, book or other product of the month clubs, with an existing sales infrastructure can use the API to add a professional-quality billing component. Tech savvy customers can also integrate FreshBooks functionality into their current workflow.

“Over the last four years, we have learned a lot about what small businesses and their customers need in order to improve the workflow, customer service and billing process,” said Mike McDerment, CEO of FreshBooks. “By making our API available, we’re helping other businesses enhance the process for delivering professional invoices over email and ground mail, efficiently tracking accounts receivable, cordially managing disputes, recording payment histories to ensure peace of mind for customers, and collecting payments online from customers.”

I spoke with Sunir Shah in FreshBooks’ Market and Communtiy Development yesterday and he told me the release of the API has three primary targets:

• import/export from existing applications, like QuickBooks.
• improving the workflow of our existing customers, through things like desktop widgets
• and the big one, providing a 21st century, professional quality invoicing and accounts receivable system for SaaS and other subscription-based services.

FreshBooks is already widely used by legal professionals, PR/marketing firms, advertising agencies, nurses, project managers, contractors, freelancers, consultants, virtual assistants, journalists, technicians, developers, web designers, graphic designers, and others who, among other things, love the idea of being able to bill clients the same day a project is finished rather than having to wait until the end of the month to squeeze an invoice out of a complicated spreadsheet or software-based accounting program.

This looks like another very smart move by our friends from the Great White North. The developers community is here.