You probably want to publish your trajectories as paths and use the Path display type in RViz to visualize them: http://wiki.ros.org/rviz/DisplayTypes/Path

On addition to the Path display mentioned by @severin, you can also use a Marker(Array) display and triplets of cylinder markers (http://wiki.ros.org/rviz/DisplayTypes/Marker#Cylinder_.28CYLINDER.3D3.29) to creade x-y-z axes, if that is what you want.

Also, it is pretty easy to create your own rviz display plugins that allow you to further customize how you want to visualize your trajectories: http://docs.ros.org/jade/api/rviz_plugin_tutorials/html/display_plugin_tutorial.html