There are several places on the internet where you can find free grammar worksheets for adult workshops. The information I have given below is for English grammar specifically.
English Grammar - The Basics
Regardless of the level at which you speak and read English (beginner right through to native), it is always good to have a strong foundation in the basic grammatical principles of the language.
You can find PDF documents for a wide variety of grammar lesson worksheets at this English language teachers resource website here. All of the resources are free to download and print! These can be used to teach all the way up to adult level.
Visual Aids In Grammar Lessons
During lessons, it can be useful to have visual aids such as videos to show a sentence being spoken or written, in order to highlight how different aspects of English grammar are intended to be used.
Check out the below video, it may be useful for those who are studying English as a second language, or even native speakers looking to brush up on their grammatical knowledge.