What kinds of maths do you know about? What level of maths are you comfortable reading? Wolfram/Mathworld offers many starting points; I would suggest prime counting functions as being very useful to think about. If you're feeling more sophisticated than that try Baez's This Weeks Finds in Mathematical Physics (www.math.ucr.edu[/url] follow links through faculty to his web page). Tim Gowers has lots of interesting ideas to think about: [url]www.dpmms.cam.ac.uk/~wtg10[/URL]