ZedSeries provides extensions for Contao cms both for end users and developers. You can contact me for any questions regarding extensions for Contao cms found on this site. A demo for most of the extensions can be found at demo.zedseries.com
There are two types of extensions:
extensions targeted to end users can be used through Contao backend and usually display it's own menu entry (or appear in frontend module list).
extensions targeted to developers aim to speed up extensions development; This type of extensions does not provide menu entry or similar, it is intended to be used in module development (i.e. while coding).