LTspice
a fast, complete, modern, unlimited Spice-compatible simulation tool
with a nice GUI for free download from Linear Technology. (Windows.. will
also run with some versions of WINE)
Evaluation Copy of CIRCAD
for DOS and Windows. Layout, schematic capture, supports reverse
engineering of scanned PCBs.
See also
Circad Lessons (beware - geocities.com) by Michele Guerra
GPIB, IEEE488, IEC625
Linux GPIB Package a
continuation of the abandoned Linux Lab project (LLP)