ZipBooks - ZipBooks is online accounting software for small businesses. 100% free, forever.
vatlayer API - Free VAT Validation & EU VAT Rates API
CountUp - Accountants for startups
MFLicenseCenter.com - Connect to fuel tax licenses for tax determination, return preparation, and reporting compliance.
Momenteo - Freelancer accounting and invoicing made simple
TaxJar - TaxJar simplifies sales tax filing for eCommerce sellers.