Spin is an ACM Award Year 2001 Winner, see here (http://www.acm.org/awards/ss_citations/2001.html).
The citation is as follows:
"For SPIN, a highly successful and widely used software model-checking system based on "formal methods" from Computer Science. It has made advanced theoretical verification methods applicable to large and highly complex software systems."
The history of Spin can be traced way back to 1980, see the history page (http://spinroot.com/spin/Doc/roots.html) for more detail.
To use Spin, see this (http://spinroot.com/spin/Man/Roadmap.html) page.
An open, cross-platform journaling program.
A scientific plotting package.