I personally developed several successful applications to support WebSphere MQ customers, which were released as freeware.
These were created as personal projects in my own time, separate to my day job at the time.
Ongoing development of these were driven by feedback received both directly from customers and on message boards and forums.
Their resulting success led to some of these being formally productised.
An extension to the administration tooling provided with WebSphere MQ to provide a greater level of feedback and diagnostic capability.
An extension to the administration tooling provided with WebSphere MQ to allow searching for object definitions across a WebSphere MQ network.
A utility application for examining the SSL configuration of a WebSphere MQ network.
A PowerShell cmdlet library for performing WebSphere MQ system administration.
I occasionally mentioned my SupportPacs on my blog.