The following is a collection of websites that is relevant to an Intermediate math classroom:

Numberphile (New to the collection -- great videos!)

Real World Math (NCTM) --New-- (There is a cost...$35.00 US for non-members.)

Wired Math: Grade 8 -- Games and Exercises

National Council of Teachers of Mathematics

NRICH: Enriching Mathematics

Yummy Math

National Library of Virtual Manipulatives

Vi Hart - Blog

9 Ted Talks to Get Your Teen Excited About Math (via MathsInsider)

We Use Math: Careers (Found via @AllenMath)