Qvacua

Qmind is a mind mapping app for your Mac which is meant to be compatible to FreeMind. It supports Quick Look. Keep in mind that it is not yet complete and in a very rough form. In addition, many things present in FreeMind are not implemented (yet). Thus, make sure to backup your files before opening and editing them with Qmind.

Jenkins Menu is a simple menu item for Mac OS X that shows the status of a (also secured) Jenkins CI server. You can configure a list of jobs that should be ignored.
(Together with dgileadi)

Qdesktop lets you set a web page of your liking as the desktop background of your Mac. You can let Qdesktop reload the page at regular intervals.

LookDown is a simple Markdown preview App for OS X. It automatically updates the preview whenever the opened Markdown document changes. It also supports QuickLook. It does not yet have a custom App icon...

LookThrough is a trivial transparent screensaver for OS X. Thus, it is only useful, when you want to lock your Mac, but want to keep track of things on the screen.

OCDiscount is a Cocoa wrapper framework for the discount Markdown parser. It is used in LookDown.

TheobromaCacao — TBCacao for short — is a small and simple dependency injection framework for Objective-C which I use in my Apps. Qmind uses TBCacao quite extensively. Have a look for a real life example.