Twitter-icon.com has a great selection of twitter icons and buttons.
Site: vtk.org (VTK - The Visualization Toolkit)
The Visualization ToolKit (VTK) is an open source, freely available software system for 3D computer graphics, image processing, and visualization used by thousands of researchers and developers around the world.
Do you have a twitter account? If so it's important
to get as many people as possible to follow you.
Great follow me icon captures attention of the visitors
and brings more followers to your twitter account.
Choose great twitter icon for you website!