I am a huge fan and advocate of basic wooden blocks. I think it helps build childrens' imaginations, sense of cause-and effect, and curiosity. But these two sets of blocks take it it to the next level.
$50 for a set on Amazon.
The other set is by Guidecraft- who have a plethora of beautiful, educational and inspiring toys for all ages and sexes. These are a great addition to any wooden block collection, as they have see-through colored partitions. You can pick up a set of $30 for $48 on Amazon.
These toys are unisex and durable, so can be passed on through the family. Great for budding architects everywhere!
Kerry, the Momster