<http://cdsweb.u-strasbg.fr/astroweb.html>:
AstroWeb is one of the most useful link collection, because
it has been developed by the astronomy community.
<http://math.nist.gov/toms/Resources.html>: The
TOMS list of web resources for mathematical software is a
collection of pointers maths software on the web.
Yahoo has managed to assemble a respectable collection of
pointers to Scientific software at
<http://uk.yahoo.com/Computers_and_Internet/Software/Scientific/>,
as well as more specific pointers to maths
(<http://uk.yahoo.com/Science/Mathematics/Software/>),
physics
(<http://uk.yahoo.com/Science/Physics/Software/>)
and astronomy
(<http://uk.yahoo.com/Computers_and_Internet/Software/Scientific/Astronomy/>)
resources.