No access to a microscope? Check out the Exploratorium’s Microscope Imaging Station — you can see videos of sea urchin cells dividing, stem cells, a zebrafish heart cell beating, and more. Any of the images here can be used in educational settings.
You can also build a cell model, and “scale up” cell and organelle dimensions to human scale. If a cell was the size of my head, how big would a mitochrondria be? Or, build a 3D diaorama inside a shoebox. One teacher uses the analogy of a school — the nucleus is the principal’s office, the DNA is the school files, the teachers are the ribosomes, the students would be proteins, and the school bus is a vesicle. Or, list a set of different analogies (the cell is like “The Simpsons”, the cell is like “a city”) and let students choose, and make their set of analogical functions.
You can also model a cell membrane using soap film. You can stick a wet finger through a bubble film, just like plasma membranes are selectively permeable. See this activity here.
This Traits of Life website at the Exploratorium has a set of online interactives and downloadable posters and articles.