Umbraco packages
Most content management systems these days have one or more ways of extending the basic system. Extending Umbraco is most often done by making a so called package.
Once you've worked with content management systems for some years, you normally have a nice set of custom add-ons for the systems, some functionality that you use often, some web user controls (if the system runs on asp.net webforms), etcetera.
I've been working on some features that I miss in Umbraco, and why not just, in the spirit of open-source software, share them with the community. As former software architect on the Synkron VIA CMS, I miss a few of the globalization/localization features from VIA, so in the near future I'll try adding some of these to Umbraco if it can be done without changing the core code.