If your students are in the midst of learning new mathematical formulas, you may consider setting up a display somewhere in the class containing examples of the formulas themselves. Make it fun, though. Don't just list formulas. Pick a theme and show examples of how those formulas can be used in everyday life. For example, if your students are learning about division, you can show a picture of three kids dividing their Halloween candy into equal amounts amongst each other.
Another idea to consider would be to place math banners all along the top of the room. On the banners, you can list times tables, multiples of different numbers, and other various study aids. Most children tend to gaze around the room throughout the day. You can give them something educational to gaze at.
Another fun item for your classroom is to display pictures all over the walls showing how math is used in our everyday lives. Cut photos out of magazines and newspapers showing careers that rely heavily on math skills. Perhaps you can show a person counting money at a bank, using money to purchase groceries, a race-car driver getting his laps timed and a fighter pilot flying a mission. When your students see the practical uses of math, they will become more motivated to learn and apply math skills.
Now matter what item you may choose, your students will be motivated. Math can seem boring to most kids but showing them how it can help them achieve their dreams will definitely get them more interested. Decide what best motivates the majority of your class and use that theme throughout your classroom.