A policies and procedures manual. No organization should operate without written policies and procedures in some form. A business-school student can be hired to do the actual assembly of the manual, and a lot of the boilerplate content can even be adapted from other companies' manuals. It doesn't have to be leather-bound with glossy pages, but it should be clear and complete. A company calendar.
Any business operation is full of time-sensitive tasks.
A company calendar can help focus everyone in the business on production deadlines, client-presentation schedules, sales trips, lead times for reordering materials and vacation times. Displayed prominently and updated on a daily basis by someone with that specific job assignment, the company calendar can help keep botched schedules and frayed tempers under control. Regularly scheduled staff meetings. Instead, it's people running around trying to find one another to get information or issue instructions. Much of that kind of communication can be handled more efficiently in one weekly staff meeting than in 20 individual encounters a day.