Instant challenges at Delightful Learning
These look fun and easy to do - they use household items so easy to put together. The instructions of how to do the challenges are very very clear.
Challenge your kids to have fun, get creative and think critically!
Recycled Creations at Wayzley Academy
This challenge is just beginning you do need to have on hand a box of recycled materials ready to use and then go for it. Aimed more at younger children would also make a good art activity.
Kids who think has a number of different challenges all designed to make you and the kids think.
Unplug your kids weekly Projects These are not very specific but still will give you some ideas of things to do.
For older children Dr Jeff's weekly challenge could be fun - you have a week to work out the solution before it is posted on the blog. These seem to be more science related challenges.
The Outdoor Hour - based on Anna Comstock's book Handbook of Nature Study. These are fun and easy to do and can be done in any order. A great place to start if you are wanting to do nature study CM style and need a helping hand to get started. (As you will probably combine a nature notebook with this time this challenge covers art as well as science and also developing important skills such as observation and memory.)
Not Weekly challenges but lots of ideas for you to use weekly
Lots and lots of drawing challenges at The Creative Journey with Karen Winters
Deep Space Sparkle has lots and lots of art lessons. These would be fun to print out a selection and add to the workboxes on a regular basis. In the left hand side bar all the lessons are organized by grades.
The Crafty Crow always has lots and lots of fun craft ideas to make. Again print out the ones you like and add to the workboxes