WOW! There are some really cool, fun, interactive math activities on the TeacherLED website. Probably about 30 in all-- I haven't been through all of them yet-- that would be great for your interactive whiteboard.
The activities are organized in the categories of Algebra; Data handling; Number, Shape, space & measure; General maths; and Spelling
The TeacherLED website and all of the resources are owned and produced by Spencer Riley, a teacher since 2002 in Birmingham, United Kingdom.
Good stuff! Check it out, you won't be disappointed.