Here's a guide to running GeoGebra 4.0 on Raspbian wheezy:
1) Flash an SD card with the Raspbian wheezy image, run raspi-config, change all the settings you want. You should enable SSH and set memory split to 128MB for GPU, and I advise you overclock the Pi (modest overclock is fine, and it won't void your warranty). After this, restart the pi, login and then type startx into the terminal. You should be presented with a GUI.
2) Unfortunately, we can't wget the official Java VM package from Oracle, so you will need to download the package to your computer and send it via SSH (use WinSCP for Windows) to /home/pi. Download link: http://jdk8.java.net/fxarmpreview/index.html
3) Once you have ssh'd the package to /home/pi, do the following in the terminal:
mkdir -p /opt
sudo tar zxvf (name of package) -C /opt
rm (name of package)
sudo /opt/jdk1.8.0/bin/java -version
You should not be presented with an error message. If this is the case, well done, you're almost there!
4) Now, you need the GeoGebra files. You have two choices:
a) You can get all the files in http://www.geogebra.org/webstart/4.0/unsigned/unpacked/ and http://www.geogebra.org/webstart/4.0/unsigned/packed/ , and then place them in /home/pi/Desktop/geogebra (which you must create first)
b) You can download a ZIP file I uploaded to FileCloud with all those files: http://filecloud.io/029kw1ug and extract it to /home/pi/Desktop/geogebra
Whichever method you choose, you should be left with the required files in /home/pi/Desktop/geogebra.
5) After this, go back to the terminal and type:
sudo /opt/jdk1.8.0/bin/java -jar geogebra.jar
And congratulations, you should be presented with GeoGebra!
(the last one is a smiley face, in case you're wondering.)