The title says it all, have you ever made any mods/plugins for any forum software? If so, what was it, and why did you feel like developing & releasing it?
For Xenforo I made the Board Message Add-on which lets you display a message to your members and guests, I originally created it for AdminBB, but I decided to release to others so they might find it useful. For MyBB I made the MyTheme Plugin which is a theme changer, it blends in perfectly with any theme, and its the only theme changer that allows you to directly link to a theme like vBulletin's theme changer.
Very Nice, my only released mod would be Tabbed Profiles for phpBB3: http://www.phpbb.com/customise/db/mod/tabbed_profiles/ I've also made my own Tabbed Statistics Mod for phpBB3 but I don't want to release it to the public because it means re-writing up the whole mod to make it Auto Mod Compatible
Do you see that user legend we have here on AdminBB? I was thinking of making it into an Add-on and release it, as XenForo does not have one.
I made a few for vBulletin. Nothing major or even nice really. They were created for my own use and released for anyone else who wanted to use them. My coding skills are not exactly great by any stretch of the imagination. But if I hack around long enough, I can usually figure it out.
I have made a ranks page mod for adapt code, plus my own userbardata mod and a paypal mod, all as my site needed them but now besides being on my oldsite I have abandoned them as fed up with developing stuff