I had some trouble to figure out how to setup and install a new windowmanager. Compilation is easy but a seamless integration is not well documented. So here's a tutorial

• get the source: http://www.fvwm.org. A nice feature you could consider to download: fvwm-themes. Very nice.
• compile and install (same for fvwm-themes if you like):

./configure && make && make install

• copy the sample config:

cp sample.fvwmrc/system.fvwm2rc /usr/local/etc

• edit the /usr/local/etc/system.fvwm2rc and find the line "AddToFunc InitFunction". Add this (this avoids the "busy cursor bug"):

AddToFunc InitFunction
+ I exec xsetroot -mod 2 2 -fg rgb:55/40/55 -bg rgb:70/50/70
+ I exec xsetroot -display $HOSTDISPLAY -cursor_name left_ptr

• create the file /etc/X11/wmsession.d/06Fvwm2 with contents:

NAME=Fvwm2
ICON=icewm-wmsession.xpm
EXEC=/usr/X11R6/bin/startfvwm
DESC=Fvwm2 desktop environment
SCRIPT:
exec /usr/X11R6/bin/startfvwm

• if you use fvwn-themes, create /wmsession.d/05Fvwm2Themes

NAME=Fvwm2Themes
ICON=icewm-wmsession.xpm
EXEC=/usr/X11R6/bin/startfvwmthemes
DESC=Fvwm2 desktop environment
SCRIPT:
exec /usr/X11R6/bin/startfvwmthemes

• create the script /usr/X11R6/bin/startfvwm with:

/usr/local/bin/fvwm2

• set it executable:

chmod a+rx /usr/X11R6/bin/startfvwm

• if you use fvwm-themes, create /usr/X11R6/bin/startfvwmthemes:

/usr/local/bin/fvwm-themes-start

• now restart your displaymanager using /etc/init.d/dm restart

This should work. If not, gimme a message in the shoutbox