I want to share with you a program I wrote recently, for visualizing vectors in 3D:
Vector Visualizer in 3D - free tool for visualizing vectors in three dimensions
You can also share the visualized vectors with others, just check "link to current vectors"
The full source code is also available for free download at:
Vector Visualizer - Silverlight tool for visualizing lines in 3D - Home
I hope you will find it useful.