I believe the version numbers listed on the firmware page for the ipw2100 sourceforge project are meant to correspond to the version of the driver that you are using. So if you are using the most current version of the driver, you would use the v0.55-current firmware.
Did you check out the links on this page?
http://ipw2100.sourceforge.net/index.php#links
There are links to rpms of the ipw2100
driver and
firmware for Fedora. Also, the link to Freakalek's How-To is worth reading, though apparently outdated. I learned A LOT about working with wireless in Linux through that page.
I have a Gateway 200ARC laptop dual-booting Gentoo and WinXP, and I have the ipw2100 wireless up an running just fine (I'm posting from the laptop, actually). I used to have Mandrake 10.1 on this computer, and wireless was a hit and miss proposition with that. Gentoo has been relatively trouble-free.