Science: buy a beginner or intermediate chemistry set and schedule regular "science parties" with one or two of her friends.  Kids enjoy hands-on activities such as making slime and modeling compounds (polymers), invisible ink (acids and bases), etc.

Math: when your daughter asks you to play a game with her, offer to play a game that makes use of math skill, such as Mancala or tangrams.  Make use of "teachable moments" to explain a math concept or a way to solve a problem using math (for example, instead of just teaching her how to calculate the area of a square, teach her how builders use the same math skills to calculate how much flooring to buy for a certain house pavement.  Real-life examples go a long way in sparking interest.

Geography: put a world globe in her bedroom and refer to it often as you discuss things happening around the world.  Lighted and colorful ones tend to grab their attention faster.  A tool that my daughter simply loves is Google Earth, so if you have a computer make sure you download this free wonderful software onto your machine.  It provides many, many hours of entertaining educational time (also make sure to check out the moon maps and the ocean views).

Use Technology: one of the best educational gifts I have given my daughter was an iPod Touch.  Of course, the Touch is not educational unless you make it to be.  There is a ton of games based on math and physics, talking dictionaries, even history- and geography-based apps, etc.  Podcasts and video podcasts are also powerful educational tools: one of her favorite podcasts is Stuff of Genius (by HowStuffWorks.com which has plenty of other great podcasts).  It discusses inventions we take for granted today, how they were invented, who invented them, etc.  It shows funny short animations to make the point and grab the attention of the viewer and is very informative.