Using your classroom's multimedia projector, you can show a series of terms. Have your students vote "monomial" or "binomial." Examples of binomials would be items like "x + 3," "y - 17," "2x^2 + 5," and so on. Eliminate students who vote incorrectly until you either have one student left or have progressed through a certain number of questions.
Give each student a slip of paper with a different monomial on it. Make sure that there are several groupings of like terms. Constants are all like terms, and so are monomials with variables to the same degree: 3x and 6x are like terms, but 3x and 6y are not, and neither are 3x and 6x^2. Have students go around the room and find their like terms, and add up to find their total value. For example, 3y + 4y + (-2y) would have a total value of 5y.
Write four different monomials on the board, and have students fill in 25-square bingo cards with various products of those monomials. If you're worried about their ability to multiply them correctly, have the students develop a list of 25 as a class. Then, call out the different products and have the students mark off the answers on their bingo sheets. Have candy or stickers on hand for the winners.
Make a series of handouts that you can tape to various parts of the classroom. At the top, write a letter from A to Z. Then put a monomial, and at the bottom put a question that would have a monomial as a result, such as: 3x * 6y^2. That answer (18xy^2) should be the monomial in the middle of a different sheet of paper, with a new problem at the bottom. Do not letter the papers sequentially, or else the students will be able to follow the problems without solving them. Give students a sheet to write down the letter and solution. Tell the students how many problems they should solve, and have a prize for the first student or students who can solve each problem correctly and end up at the starting letter.