Are there any solutions for OpenBSD to just:
Insert the custom installer CD, press enter (like: "are you sure?" – message), then the installer automatically partitions the disk/installs OpenBSD, and then customize it a little (ex.: install a few apps from ports)?
This can be done using Kickstarter for RHEL. But can it be done for OpenBSD? I googled for it and didn't found any good answer yet (only that needs bigger programming skills..).
Best Answer
An OpenBSD install does most of that currently, but you just have to press "enter" a lot. As for doing the pkg_installs and other customizations, there is (and has been for a long time) a mechanism to do that, although it's harder to track down the documentation if you don't know what you are looking for. The installer will pull a sitexx.tgz or sitexx-hostname.tgz install set if it is on your installer source.
The FAQ has a lot of details here: http://www.openbsd.org/faq/faq4.html#site
The one other big tip I'll give you that is also mentioned there is the rc.firsttime(8) script mechanism. If you drop a file at /etc/rc.firsttime, those commands will be run at the next boot and then the file is deleted. If doing so in the installer, append to that file, since the installer uses it to.
I saw some rumblings on the mailing lists that a developer is working on an even more automated mechanism for the installer too...
UPDATE 2014-05-01 -
autoinstall(8)Automatic Install ability included in 5.5: http://www.openbsd.org/55.html