Trunk syncs your inventory in real-time across different sales channels like Amazon, eBay, Etsy, Faire, QuickBooks Online, Shopify, Squarespace, Square, Tundra, and WooCommerce. Trunk also gives you powerful centralized inventory features like bundles and kits that sync and adjust like magic. Trunk strives toward the vision of making it easier for businesses to sell on multiple platforms without the overhead and pain.
TurboCASH - TurboCASH Accounting Free and Open Source Accounting Software for Small to Medium Business.
BOMIST - Parts Inventory and BOM Management for Electronics
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
PartKeepr - PartKeepr is an open source inventory management system that you can alter according to the particular requirements of your business or of the area from where you are operating.
Xero - Xero is online accounting for your small business.
Sellbrite - Multichannel ecommerce management for serious sellers.