Pre-requisites

Components that Gnome15 will always require, regardless of configuration

GTK based desktop, or a desktop that will run GTK applications with the correct packages installed, such as KDE.
Python - Programming language. Gnome15 was developed with Python 2.6
PyGTK - Python GTK bindings (including Python GNOME bindings, Python GObject bindings, RSVG bindings).
DBUS - Python bindings.
LXML - XML parser.
Python Cairo - Python bindings for the Cairo graphics library. Note, for best performance on the G19 you will need at least Cairo version 1.8.3.
PIL - Python Image Library.
Python X Library - Interface for Python to the X11 Protocol.
PyInotify - File modification notification.
PyUSB - Python USB library.
Python uinput - Access uinput system from python.
Python Keyring - Cross platform keyring manager

Compnents that add functionality to Gnome15.

GNOME - The free desktop. You may then use the GNOME plugins for extra integration with the Evolution and other GNOME components.
setproctitle - Allows a process to change its title.
Python Appindicator - Allows Gnome15 to add an indicator (replaces applet).
Python WNCK - Python bindings for the WNCK library (must be installed when BAMF is not available for automatic macro profile switching).

Components that are required by the various plugins.

evolution-python - Python Evolution bindings. Used for Calendar plugin.
vobject - Python vCard and vCalendar parser and generator. Used for Calendar plugin.
PyAlsa - Python Alsa bindings. Used to monitor mixer events for volume plugin.
MPlayer - Movie player. Used by the lcdshot plugin to encode video.
FFTW3 - Fourier transform library used by the Impulse15 plugin.
Pulse - Sound server. Required by Impulse15 plugin.
PyGST - Python GStreamer bindings (Media player).
Python GData - Python bindings for Google Data API (for Calendar, Analytics).

Components that vary depending on your hardware.

pylibg19 if you have a G19.
kernel driver if you have a G19, G13, G110 or G15. You will also need python-inputevent.
g930 driver requires python-inputevent only.
libg15 - Library for G15 and compatible keyboards. Full support for newer models such as the G110 and G510 requires the most recent g15tools SVN code and a patch available on this site. See here for discussions about the G510, here for the G510 patch. Also, see here for discussions about the G110. You will also need this patch to be able to set the keyboard backlight color. To avoid having to patch libg15 yourself, you can use the packages in the Gnome15 repository for your distribution.