While monitor functionality is present in the ipw2200 driver since 2.4.15, Kconfig does not contain the option to allow you to enable it. This patch fixes that. As it's a simple configuration change can we include it the gentoo-sources until it's included upstream? It's based on an email I saw from James Ketrenos <jketreno <at> linux.intel.com> (His patch was for the 2100).
Monitor mode in ipw2200-1.0.8 (which is what is present in linux-2.6.15) is partly broken due to bugs in firmware version 2.4, and should thus not be enabled. Should you wish to use monitor mode, please use the external ebuilds.