Place posters on a theme, such as a construction site, firehouse or grocery store, in the block play area. Periodically change the theme. Supply props that match the posters, such as toy construction trucks, plastic fire fighters' hats or a play shopping cart. Talk with the children about the theme and allow them unstructured time to play with the blocks. Occasionally, acknowledge what they are pretending to be. If Sally is pushing the shopping cart full of blocks with her "baby" in the seat, ask her what her baby's name is or what she is buying for dinner.
Collect multiples of several sizes of one shape of unit block. Tell the children to sort the blocks into piles according to their size. Ask each child to pick one block of each size. Explain that you would like each child to place his blocks in a line, from the shortest block to the tallest. Have them switch the order, from the tallest to the shortest. Ask the children to point to the block that is first in line, second in line and third in line.
Make a pile of several of each type of block in the center of the play area. Set aside one block of each type. Ask each child to choose a block from the pile. Place the blocks you set aside in a line. Ask the children to place their blocks by the matching blocks in the line. Encourage them to notice similarities and differences in the blocks.
Find objects around the room that can be measured, such as a table top or bookcase. Ask the children to lay blocks of the same size, end to end, as the length or width of the object. When they are finished, tell them they are measuring how long, or wide, the object is. Ask them to count the number of blocks they used for their measurements
This activity works well at cleanup time. Set out three or four laundry baskets or other containers. Pick one size, or shape, of block to place in each basket. Tell the children to look for blocks that match the ones in each basket and to pick the blocks up and place them in the appropriate basket. The children will learn sorting as they pick the blocks up from the floor.