Desktop Data Manager is a clipboard manager for GNOME similar to Klipper for KDE. With DDM, it is possible to display different types of content like text or images. Additionally, DDM includes a screenshot taking application which is able to take screenshots of a single window or subwindow, a rectangle of the screen, or the whole desktop.
Dia is a program for creating diagrams of all kinds. The current version can do UML class diagrams, Entity-Relationship modeling, network diagrams, and much more. The engine is very flexible and dynamically loads diagram-types from disk. It stores diagrams in an XML format, but can read and write a number of different formats.
DiaCanvas is a generalized version of the drawing canvas used by DIA. It extends some features used by DIA and adds new ones, while preserving as many of the original features as possible. This project is no longer actively maintained. It is suggested that you try DiaCanvas2 instead.