Often, but not always, working with students with disabilities. I used to support the visually impaired, sometimes individually, sometimes in small groups. It covered all sorts of stuff like getting course materials in suitable formats, proof-reading work, assisting in the cafeteria, acting as amanuensis in exams etc etc.
Other people doing the job with learning disabled students also did things like supporting in class (under the tutor's guidance), helping clients to use the toilet, making sure they got their transport home.
In both areas, it's a matter of generally being a helpmate around college - someone students can go to in the first instance if they have any problems.
It's very rewarding work, and can be a step towards becoming an SEN lecturer. Friend of mine began helping out with a basic skills class and ended up as course leader.