Hi misstiredbuthappy:
First thing to come to mind is OXFORD OWL: www.oxfordowl.co.uk/for-home
There are maths & reading sites - with tips about what you can do at home to help, ideas, games, e-books, etc...
Great place to start off - just caught it with DD2 - but it seems to be improving and improving. It's through Oxford University Press.
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CBEEBIES alphablocks is fantstics - you can see all the old programs and the songs are worryingly catchy (I've caught myself humming them at work). - www.bbc.co.uk/cbeebies/alphablocks/ - very good for building those phonics skills without even realising it.
CBEEBIES NUMBER JACKS is also good for Year R: www.bbc.co.uk/cbeebies/numberjacks/
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A school in Poole has some very useful resources for Year R here: www.lilliput.poole.sch.uk/Curriculum/Year+R+Resources
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Useful things to be doing at home:
Measuring (have your DC help with cooking and have them measure oil/ water/ weigh flour/lentils etc...)
Counting: Well snakes and ladders is fantastic. Great counting on skills there - when good to 6 (one die) add a second die to get good to 12. When you're great at adding on (don't need to count - but can just do it) - play it backwards to work on subtraction (start one die and then add second die).
Shape: Look around the house for circles, squares, triangles, etc... Use a chocolate box - say quality street - to discuss shapes.
Try to learn names for 3D shapes like sphere (balls/ oranges/ the sun/ planets), pyramid (Giza pyramids, tea bags, toys), cubes (foot rest/ boxes), cuboids (sofa/ cereal box).
Remember that reading to your child is also important - they learn the rhythm and sound of words. Let them see you read - use your finger so they can follow what you're reading on the page. Don't worry if they can't read much yet - it will come. Just keep reading away.
HTH