Here's a link to wabsite with some interesting maths projects and investigations that I've been using. Some of the stuff needs modifying for relevance or simplifying a little, but there are some useful additions to the normal text book stuff:

http://illuminations.nctm.org/

A few other bits and pieces that I've found were from these sites:

http://www.emaths.co.uk/index.html has some nice stuff for the interactive whiteboard.

http://www.mathsroom.co.uk/downloads.htm has some other bits and pieces that I've used.