squeeze() if you want to delete all unit dimensions (provided that the matrix is at least 3d).
permute() the dimension out of the way if you want to move a specific dimension.
For example,
M = rand(1,250,1,500);
size(squeeze(M)) %gets rid of both 1's, leaving 250 x 500
size(permute(M, [2 3 4 1]) %moves dimension 1 to the fourth dimension, leaving 250 x 1 x 500 x 1 but the trailing 1 is not displayed so 250 x 1 x 500
