Wolfram Alpha

http://www.wolframalpha.com/

This is a resource I used a lot during my undergrad, as basically a repository of all knowledge. Have a question? Type it into Wolfram Alpha and you will probably get an answer. It will do calculations, find derivatives and integrals, give you statistics and a whole lot of other things as well.

Wired Math

http://cemc2.math.uwaterloo.ca/wired_math/
This is a website I found that has all kinds games and lessons for grade 7, 8, and 9 math. It is hosted by the University of Waterloo, and everything is sorted by grade as well as topic. I think it is well worth having a look at.

Derivative Plotter
http://mathdl.maa.org/images/upload_libr ary/4/vol4/kaskosz/derapp.html
This is a great little applet I found while tutoring my sister. It allows you to enter any function and plot it. You can then move the slider and it will gradually graph the derivative and show you the tangent line on the graph. There are also a lot of demo graphs as well.

Sites for Teachers
http://www.sitesforteachers.com/
This is an interesting site that I found that is a database of websites that might be useful as teachers. I haven't been through it extensively yet, but there is a lot there.

Handley Math page
http://www.pleacher.com/handley/mhome.html
This is a neat little website I found that has some resources such as lesson plans, but I find its real value is in the math humour and puzzle section. There is some pretty funny and clever stuff to help you spice up your lesson.