Here is a really cool YouTube video, Cells Cells-Parts of a Cell Rap, that describes the parts of a cell in a very simple and rhythmic way. This video may be more suitable for upper elementary to early middle school students.
My students always seem to enjoy this song, and my suggestion is that you take it the way that you feel is right for your class or students. For example, in my case, I first introduced the students to the main parts of all cells: the building blocks of multi-cellular organisms. Then, make sure to give your class a copy of the lyrics, and try and sing it with your class. After you have tried singing it with my students I then unleashed this video on them for a few days while we talk about cells-they will follow along with their lyrics if you decided to give them a copy. Finally, I give them a task to create their own song or poem to go with the parts of a cell. Enjoy!