Here's how to get ikiwiki. See setup for how to use it, and be sure to add your wiki to IkiwikiUsers if you use ikiwiki.
tarball
The best place to download a tarball of the latest release is from http://packages.debian.org/unstable/source/ikiwiki.
Installation steps and requirements are listed on the install page.
packages
To install with apt, if using Debian (since 4.0), or Ubuntu (since 6.10):
Note that Debian 4.0 and especially Ubuntu 6.10 contain older versions of ikiwiki, there have been lots of enhancements and bug fixes since those versions.
apt-get install ikiwiki
Or download the deb from http://packages.debian.org/unstable/web/ikiwiki.
There is a backport of a recent version of ikiwiki for Debian 4.0 at http://packages.debian.org/etch-backports/ikiwiki.
There is also an unofficial backport of ikiwiki for Ubuntu Hardy, provided by Paweł Tęcza, at http://gpa.net.icm.edu.pl/ubuntu/.
NetBSD and many other platforms: pkgsrc has an ikiwiki package.
FreeBSD has ikiwiki in its ports collection.
Gentoo has an ebuild in its bug database.
IkiWiki can be installed from macports
by running sudo port install ikiwiki.
revision control
Ikiwiki is developed in a git repository.