JSON API to integrate with QuickBooks Enterprise / QuickBooks Desktop
https://qubesync.com
Spent 14 years slogging through a custom implementation with my previous company, and didn't want my pain and suffering to go to waste. Just spent a few hours yesterday to replace that app's integration with my new api and got a pretty good diff:
117 files changed, 258 insertions(+), 10032 deletions(-)