Amüsante Links:

• mathematical biographies
• compute your Erdös number. Mine is 5, and the path is Schröer, Huybrechts, Götsche, Zagier, Odlysko, Erdös.
• Mathematics Genealogy Project.  Mine is Flenner, Storch, Behnke, Hecke, Hilbert, Lindemann, Klein, Plücker, Gerling, Gauß...
• tips for authors (by James Milne)
• Wie halte ich einen Seminarvortrag? Wie bearbeite ich sinnvoll ein Übungsblatt? (by Manfred Lehn)
• Grothendieck circle
• millenium prize problems
• Hilbert's problems
• Fields medal
• earliest known usage of mathematical words
• Oberwolfach photo collection

Buchtips:

• Paul Halmos: I want to be a mathematician. Springer, Berlin, 1985.
• Nicholas Bourbaki:  Elements of the history of mathematics.  Springer,  Berlin, 1999.
• Constance Reid: Hilbert.  Springer, Berlin, 1970.
• Ioan James: Remarkable mathematicians. Cambridge University Press, Cambridge, 2002.
• Edwin Abbot: Flatland. Penguin  Books, New York,  1984.
• Imre Lakatos: Beweise und Widerlegungen. Vieweg, Braunschweig, 1979.
  
• Steven Krantz: A primer on mathematical writing. American Mathematical Society, Providence, 1997.