Building toys are great for hand-eye coordination, imagination, visual motor skills, perceptual skills, grasping strength, manipulating shape orientation, sorting colors/shapes and gross motor movements to name a few.
You can scatter the pieces around the room so your child has to move around for them. If they are walking they can practice squatting to pick up pieces or moving from crawling to standing to reach up high. If you are using legos they can work on stabilizing themselves in space (balance) while having to pull apart the pieces (upper extremity strength). Also, they can work on their body awareness because if they bump into their masterpiece it could topple over and then you have to start all over again.
To encourage standing for a child who is not yet confident in their standing skills you can build the structure on your coffee table so they have to pull to stand for each piece. To increase waking you can have the other pieces on a couch a little bit away from the coffee table so they have to transition between the two support surfaces to get new pieces.
There are a ton of great building toys out there. I will do my best to name the ones that I can think of but feel free to add other ones that you know about.
Please share your favorite building toys!