I'll be honest here .... probably around $2000

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We are eclectic homelearnings with a definite unschooling streak.
If I had to break down my estimation of spending this year it would be something like:
Books $500 (everything from novels, history books and interesting looking science books to spelling workbooks and math books)
Board games $300 (We love board games and this year have bought 10 Days in Asia, 10 Days in Europe, 10 Days in Africa, Artifact, Carcassonne, Carcassonne Tower expansion, the Ungame, Castle Keep and Squiggle)
Science experiments/activities $300 (Luke loves those things where you excavate the dinosaur bones and he blasts through science kits in no time)
Art supplies $150 (Sculpy, paints, pastels, crayons, wooden model building kits)
Classes $750 (Luke has taken 3 very expensive series of classes on Flash animation, video game design and web site design.)
iPod $160 (Luke spends hours watching National Geographic and other podcasts, listening to music and listening to audiobooks so I consider this an educational expense.)
There are still a few months of this 2007/2008 "school" year left so I expect our total will hit around $2000+ once we are all done.
We also visit the library at least one a week and use the internet heavily. Luke is an information junkie and he just blasts through stuff as fast as I can get it to him. Our library is a small regional branch about the size of my living room which is why our book costs are so high.