Split up the class into groups of two. Write down the names of people who relate to current classroom topics: historical figures from the time period being studied, scientists in the field you are currently investigating or fictional characters from books the class is reading. Have each pair draw a name. Then, each pair will work together quietly coming up with a list of questions and answers to create an interview with the person. Give the students time to prepare, and at the end of class, allow each pair to come up and present the interview. One person will be the famous person or character and the other will be the interviewer.
Write a broad topic or theme on the chalkboard and set a timer. Have the students see how many items they can list for that topic on a sheet of paper before the timer goes off. Whoever has the most items listed when the timer goes off wins. Make sure the students' items are all correct. Reward the winner with a small prize. Topics could include things such as United States presidents, cities and towns in your state, or careers that require math skills. Keep a list of topics on hand so that this game can be played at the last minute.
Split the class into two groups. Instruct each student to cut a piece of paper into four pieces and write a trivia questions on each piece of paper. These questions should be based on current classroom topics. Students can use their text books to make sure they have the right answers. After a set amount of time to create the questions, collect each team's trivia. Use each team's questions to quiz the other team in any trivia-style game of your preference.
Sponge activities for times when the teacher needs quiet to do certain tasks are a little bit different. For these times, keep a file of fun but educational worksheets on hand. For example, Mad Libs-type worksheets are funny but also help students practice their parts of speech. Crossword puzzles and word searches are other great worksheets to keep on hand. Journal writing or short essays on fun topics can occupy students quietly as well. Keep a selection of lighter reading materials on hand for quiet reading.