According to fluxbox documentation to have apps startup with fluxbox you just add the the command to ~/.xinitrc. Because I use KDM as my dm I don't have an xinitrc.

If I simply created an xinitrc in ~/ and added the commands in there (e.g. gkrellm & ) would that be enough to make those programs startup with fluxbox?

I don't think so - the ?dm programs ignore ~/.xinitrc AFAIK. I think ~/.Xsession is the file they pay attention to. So that may work.

Doesn't flux have a 'startup' file now? You could just add the programs you want there, I believe - ~/.fluxbox/startup or something.

In your /.fluxbox dir.... You should a startup script if not make one .
Seee Xample below of a fluxbox startup script...!!!!


# fluxbox startup-script:
#
# Lines starting with a '#' are ignored.

# You can set your favourite wallpaper here if you don't want
# to do it from your style.
#
# bsetbg -f ~/pictures/wallpaper.png
#
# This sets a black background

# /usr/X11R6/bin/bsetroot -solid black

# This shows the fluxbox-splash-screen
fbsetbg -C /usr/local/share/fluxbox/splash.jpg

# Other examples. Check man xset for details.
#
# Turn off beeps:
# xset -b
#
# Increase the keyboard repeat-rate:
# xset r rate 195 35
#
# Your own fonts-dir:
# xset +fp /home/navaboy/.font
#
# Your favourite mouse cursor:
# xsetroot -cursor_name right_ptr
#
# Change your keymap:
# xmodmap ~/.Xmodmap



# Applications you want to run with fluxbox.
# MAKE SURE THAT APPS THAT KEEP RUNNING HAVE AN ''&'' AT THE END.
#
# unclutter -idle 2 &
# wmnd &
# wmsmixer -w &
# idesk &
# wmdrawer &
# wmxmms &
# wmcpuload &
# wmclockmon &
# wmix &
# wmmemfree &
# xcompmgr -c &
# gkrellm -w &

# And last but not least we start fluxbox.
# Because it is the last app you have to run it with ''exec'' before it.

exec /usr/X11R6/bin/fluxbox

newer versions of fluxbox have an "apps" file in ~/yourname/.fluxbox/apps

add a program to startup by adding this to the apps file

[startup] {program name here}

[edit]
same as detpenguin said, he just types quicker