Examples of sites with particularly recommended math games include MangaHigh.com, Illuminations.nctm.org and Funbrain.com. Good math games for girls are the same as those for boys, and the resources available online are extensive. The key is to find games with effective skill progression, attractive graphics and game design.
Math games need to be engaging, introduce concepts clearly and allow students to develop skills through practice. Sites with themed games and attractive graphics are particularly useful, as these engage students more effectively. However, themes divided by gender are less useful than themes that focus on the interests of the pupil in question, as every student is different.