The latest version of IPCop is v2.0.6.
(This is the lastest ISO to make an install disc. Updates can be installed from the Updates page in the web admin GUI.)
The latest previous version of ipcop is v1.4.21, but you first need to download v1.4.20 from sourceforge on ISO, burn this to a CD and install and then upgrade to v1.4.21.
Full download and installation instructions can be found here (ipcop.org).
See the list of ipcop mods for links to external addons. Note: Some addons are wholly unsuitable for use on a firewall and their use WILL reduce your security. When requesting support on this site, we will often ask you to reinstall without addons to check that your config is valid. Some addons will break your ipcop.