Try this: When a key employee is hired, have other employees who will be working with that employee bring something in about themselves. Each of these veterans will give this object to the new kid on the block to hold on to permanently.
It could be a magazine article that person recently read and enjoyed; a photo; a joke; food; or an item they built or broke in the back of the plant.
The new employee will have something tangible to keep, allowing this new hire to remember not only each person introduced, but something unique about them. And it will be something good to laugh at a few months down the road.