Links for mathematics: (see also here )
 

Math. Departments Servers List (Very useful!)

Karte von WWW-Servern mathematischer Fachbereiche und Fakultäten (Germany only, of course)

Classification Systems (Karlsruhe) (Searchable index)

Mathematics Calendar (maintained by AMS)

Mathematisches Forschungsinstitut Oberwolfach   / Mathematical Sciences Research Institute

Newton Institute Home Page / Institut Mittag-Leffler

Sloane's On-Line Encyclopedia of Integer Sequences (You name it, Mr Sloane probably got it!)

History of Mathematics (Lots of biographies including pictures and references)

Mathematical Quotation Server

GAP - Groups, Algorithms and Programming.

FDLIST- Information list for representation theory of finite dimensional algebras

Broué's abelian defect group conjecture (Page maintained by J. Rickard)

Dade's conjectures (Page maintained by K. Uno & J.B. Olsson)

Dave Benson's Home Page (Includes an impressive preprint archive on Groups, Representations and Cohomology )

Kate Fenchel / Richard Brauer (Persons who have influenced me)

Allgemeines zur Mathematik (D. Bargman, Kiel)

 John Conway's Game of Life (in Java)

Mathematical Fiction Homepage  (Compiled by Alex Kasman) ) 

Formens evige Magie (by Hans Christian Andersen)