We registered and received some great foam blocks for our baby shower, but I really wanted Kate to have some larger blocks to go with them. But, those nice, big, cardboard blocks cost around $30 (or more depending on how many you get).
Luckily we didn't need to buy any. We had everything we needed to make our own.
Some card boxes from Adam and some tape (I used book tape because it is thicker/stronger than regular packing tape).
That was all. Basically free blocks for Kate. And as Adam gets more cards for work, Kate gets more blocks for play :)