Packages for common geometric calculations including the ROS transform library, "tf". Also includes ROS bindings for "bullet" physics engine and "kdl" kinematics/dynamics package.
Xacro is an XML macro language. With xacro, you can construct shorter and more readable XML files by using macros that expand to larger XML expressions.
Allows one to create "nodelets" -- ROS node-like entities that run within the same process so as to avoid IPC and serialization overhead
Provides a standardized interface for interfacing with preemptable tasks. Examples of this include moving the base to a target location, performing a laser scan and returning the resulting point cloud, detecting the handle of a door, etc.
ROS-independent library for dynamic class (i.e. plugin) introspection and loading from runtime libraries
ROS communications-related packages, including core client libraries (roscpp, rospy, roslisp) and graph introspection tools (rostopic, rosnode, rosservice, rosparam).
Packages related to gathering, viewing, and analyzing diagnostics data from robots.
Package used to retrieve resources of different kinds, e.g. http://, file://, the ROS specific package://, etc.
Allows you to publish the state of a robot (i.e the position of its base and all joints) via the "tf" transform library
Contains packages for modeling various aspects of robot information, specified in the Xml Robot Description Format (URDF). The core package of this stack is urdf, which parses URDF files, and constructs an object model (C++) of the robot.