Get a new maths question to solve every day of the year with this superb site. It's great for lesson starters and the answer and explanation can be shown with the click of a button. Search questions for other dates by clicking the link at the bottom of the screen.
http://ictmagic.wikispaces.com/Maths
This video is taken from the iTunes Visualiser called Jelly that makes pretty patterns that react in real time to the music that is playing. The patterns produced show rotational symmetry and could be used as an excellent resource in a starter or plenary on the topic.