!! PROBLEM SOLVED !!
I'm trying to get Compiz working on Debian 5.0 with Intel GMA 3100. I've installed compiz and libgl1-mesa-dri, then I restarted X with ctrl+alt+backspace and did compiz --replace in terminal which gave me this:
Checking for Xgl: not present. Detected PCI ID for VGA: 00:02.0 0300: 8086:29c2 (rev 02) (prog-if 00 [VGA controller]) Checking for texture_from_pixmap: not present. Trying again with indirect rendering: Checking for texture_from_pixmap: present. Checking for non power of two support: present. Checking for Composite extension: present. Comparing resolution (1280x1024) to maximum 3D texture size (2048): Passed. Checking for nVidia: not present. Checking for FBConfig: present. Checking for Xgl: not present. Starting gtk-window-decorator /usr/bin/compiz.real (core) - Warn: SmcOpenConnection failed: Could not open network socket /usr/bin/compiz: line 393: 9053 Segmentation fault ${COMPIZ_BIN_PATH}${COMPIZ_NAME} $COMPIZ_OPTIONS "$@" $COMPIZ_PLUGINS
SOLUTION
In terminal:
aptitude install compizconfig-settings-manager libcompizconfig0 python-compizconfig
compiz --replace
and according to http://wiki.debian.org/Compiz
echo "export WINDOW_MANAGER=/usr/bin/compiz" >> ~/.gnomerc
to make it start automatically.
Install compiz-fusion-plugins-main and compiz-fusion-plugins-extra for more plugins.