Having somewhere to store your tools is key to maintaining the workspace.
Shelves
A good sturdy shelf, installed on the appropriate brackets, can handle quite a bit of weight, and give your tools a home when not in use. They can be metal or wood, of many different lengths, and can be installed under the table top with an all wood workbench. Metal workbenches have arms that extend above the table surface, and can accommodate shelves there as well.
Drawers
For any and all storage and organizational needs, drawers are invaluable. Deep or shallow, custom designed for specific items or a catch-all, adding one or more drawers to your workbench will put tools, and things like screws and nuts, at your fingertips. They install easily under the table top, ready for storing your things.