There are so many fun math sites with games, manipulatives, and cool project ideas! Find a few here!
Fun Investigations games can be found online at http://investigations.terc.edu/library/Games_23.cfm (2nd-3rd grades) or http://investigations.terc.edu/library/Games_45.cfm (4th-5th grades).
http://www.mathplayground.com/ - This site is full of fun math games and videos! There are also logic games if you love the challenge of figuring things out or solving mysteries (click on the green "Logic Games" button at the top).
http://nlvm.usu.edu/ - This incredible website has all the manipulatives you could want online! There are puzzles such as tangrams, patterns, number puzzles, and games. There are manipulatives that help to make sense of a math topic you are learning, such as fraction strips, pattern blocks, base ten blocks, geoboards, and pentominoes. If you like computer programming, try to move the turtle or ladybug through a maze or to a pond. Have fun exploring!
http://mathforum.org/students/elem/ - Do you love math? At this site you can talk to other kids about math, play games, take online field trips, discover math projects you can do, challenge yourself with problems or puzzles, or get help with your math homework.
http://www.coolmath.com/ - This popular math site has incredibly fun math games! They are so fun it is sometimes hard to believe they are educational! Run a lemonade stand, drive a crazy taxi, practice your math facts with games, improve your visual thinking skills, and more. There's also a math dictionary and math lessons available for you to grow in your mathematical understanding.
http://www.mathsisfun.com/ - This site has games such as Connect Four, mazes, jigsaw puzzles, Chess, Checkers, and the Tower of Hanoi. There is a math dictionary and lots of math activities or worksheets you can do to learn!
http://pbskids.org/cyberchase/math-games - This PBS Kids site has a variety of fun math games you can play to practice what you are learning and have fun at the same time!
http://www.mathcats.com/index.html#contents - Math Cats is a unique website because there is a math art gallery, math crafts, and math in real life that you can find here!
http://cte.jhu.edu/techacademy/web/2000/heal/mathsites.htm - This site is packed full of math games, puzzles, problems, brain teasers and more! Wow!
http://calculationnation.nctm.org/Login.aspx?ReturnUrl=%2fGames%2fdefault.aspx - Calculation Nation has some excellent, challenging math games that are guaranteed to make you think and grow!
http://illuminations.nctm.org/ActivityDetail.aspx?ID=204 - You can create your own bar graph here.
http://illuminations.nctm.org/ActivityDetail.aspx?ID=12 - The Factor Game is a great way to practice your math factors!