I love these blocks! They are on the pricey side, but they are sooo cool. Get them here.
I recently purchased two sets of blocks. One set is by Haba and they are available here.
They next set I found on ebay. Vintage, American made Holgate Toys blocks. New they would run about $60+ but I scored them for about $10. They were unused, dead stock from the 1950's. Fab find. You can find them new here.
I love seeing my boys play with blocks and use their imagination. A plus for me is that I love the sound they make as they are played with, and when we gather them up to put them away, they "clack" against one another it's such a great sound. A better alternative to blinking lights and the annoying sounds of most battery operated toys.