If you want a great resource for your Montessori school, homeschool, co-op, or even just for your primary-school aged kids in general, then this is it. Hundreds and hundreds of .pdf printables at your fingertips.
Bought separately, you'd spend over $3000, but the CD-ROM is available for just under $600. Once purchased, you can continue to purchase future files that she makes for 50% off. Visit the Montessori for Everyone website.
I tended to use the 3-part cards. These are brightly coloured pictures, words, and a third card with pictures and words together. Once you print them out on card and laminate them, then your child can practice matching the pictures and the words together, and then check them with the "control" card to make sure the answers are correct.
That makes these items self-correcting, which is great for a child's learning and independence.
BTW, I've had to withdraw the offer to give my copy away free: it infringed Lori's T&C's.