Here's a cool trick for the Finder if you use it Columns view. When you are changing the width of a column, you can hold down the Apple (or command) key when moving the column and all of the columns widths will be adjusted. Finder will not normally remember your columns widths; once you close the Finder window and open a new one, the columns widths will revert to their original values. But if you adjust the column widths in Finder while holding down the Apple (or command) key, Finder will remember these widths when you open new Finder windows.