This website has great animations (fun too!) that cover a wide range of topics. You can do a free 5 day trial and would then need to subscribe to it. I think it is worth it!
RefSeek's guide to the 25 best online resources for finding free educational videos. With the exception of BrainPOP and Cosmeo, all listed sites offer their extensive video libraries for free and without registration.
This is a superb game which teaches about food webs in a competitive battle game. Who will succumb to selection pressures and who will survive?
http://ictmagic.wikispaces.com/Science
Play battleships along a numberline using a variety of maths skills, including fractions, decimals and measurements.
http://ictmagic.wikispaces.com/Maths