Used to visually show summary of a process and each of the components or relationships involved in the completion of the process. See: http://en.wikipedia.org/wiki/Process_flow_diagram
Cause and Effect Diagram (a.k.a. Ishikawa Diagram)
Used to explore why something happened or might happen by breaking up the issue into smaller categories. It can show relationships and contributing factors. See: http://en.wikipedia.org/wiki/Ishikawa_diagram
Decision Tree
Can be used to either predict or describe possible outcomes and decision points that occur chronologically. See: http://en.wikipedia.org/wiki/Decision-matrix_method
Flowchart
Provides a visualization of a system or process using symbols to indicate the start or endpoint, linked relationships, input and output milestones, process steps, and decision points. See: http://en.wikipedia.org/wiki/Flowchart
Function-Block Diagram
Used to describe current systems or workflows and to then compare it with a proposed system or workflow. See: http://en.wikipedia.org/wiki/Function_block_diagram
Interrelationship Diagram
Used to illustrate how different issues are related to on another based upon cause and effect. It helps to determine which issues are causing problems and which are an outcome of another action. It can be displayed to show the strength of each influence in a process. See: http://en.wikipedia.or/wiki/Seven_Management_and_Planning_Tools
Step Chart
Used to show a procedure or a change in value over time using a series of boxes, each representing a step or procedure. Can be helpful for planning a project and identifying the ordering of tasks.
Swim Lane Diagram
A type of flowchart used to display grouped objects in categorized columns. See: http://en.wikipedia.org/wiki/Swim_lane_diagram
Timelines
Summarizes the steps or events of a process of project over a specific period of time. It consists of a horizontal bar representing time progressing from left to right with a series of boxes aligned to when a given event or process should be completed. See: http://en.wikipedia.org/wiki/Timeline