I'm an accomplished person in my field, but don't have any degree. Would I be able to be a teacher or substitute? As far as I'm aware, the base requirement to be a teacher or substitute requires a degree. However in my case, I've been working in my career field for going on 10 years. I'm wondering if it's possible to move to Academia, either part-time or full-time without having a formal college degree.

Lately, I've been having an "itch" to impart my own experiences and knowledge on students that are just starting out. I haven't decided on what exactly I want, but it could be anything from a guest speaker to teaching a full-time class.
Traditionally, most higher education faculty positions require advanced degrees and usually terminal degrees (e.g., PhD, MD, Master of Fine Arts) and lectures at universities often have master-level degrees. 

Some universities now have "Professor of Practice" positions (e.g., UCSB for people with non-traditional backgrounds. (Hat tip to Buffy for this feedback). 

Community/Technical colleges often have faculty with less formal education. Although faculty often hold PhDs, many have master's degrees. However, for some technical, trade positions less formal education is required. For example, browsing Google jobs for "welding instructors" show many positions that require an associates degree plus experience.  

Usually, guest speakers have no formal requirements other than being invited by the course instructor.