Did you use the Diagram tool in MS Office, and trying to find similar functionality in OOo? Though OOo doesn't have a Diagram Gallery (see Figure 2) like in MS Office, you can still manually create comparable diagrams (see Figure 3). You can create an organizational chart for your team at work or an organization you belong to, make visuals of technical processes, or even create your own food pyramid; whatever floats your boat. Some diagram types may take a bit of time and creativity with the basic building blocks, however, some types like organizational charts and radial diagrams you can easily create by throwing a few shapes down and squeezing in a few connector lines.
When you want to start creating a Diagram, you need to make the Drawing toolbar visible by clicking View -- Toolbars -- Drawing. You can do this in Writer, Impress, or Draw; however (for reasons I'm not sure of) the Drawing toolbar in Writer lacks the special line connectors that make it much easier to connect shapes and objects. If you want to make an organizational chart or diagram that contains shapes connected by lines for use in a Writer document, you can create it in either Draw or Impress and then copy the final product into Writer.
Once you have the Drawing toolbar visible, you can start plopping down shapes. You can insert text within the shape by double-clicking it and typing. If want to connect the shapes, choose a line style from the Connectors, hover over a object or shape, click and hold down the mouse button until you're hovering over the other object you want to run the line between, and then release the mouse button. If you want to change the spots the lines connect to, select the line connector, click and hold the mouse button, and drag it to another connector point or a different object, and then release the mouse button. Once you have the basic diagram built, you can make any desired formatting changes; for example, sizes and colors for the lines and shapes.