Qminder - Qminder works the way it sounds: It helps a company mind its queues.
Queue-it - Queue-it empowers organizations to deliver seamless user experiences and protect their brand reputation by controlling online traffic.
slashQ - Queue management system
QLESS - QLESS offers queue management software solution.
Zeplo.io - Message queue as service.
TotalQueue - TotalQueue offers complete customer queue management software solution.