How can I access more than one monitor, mouse and keyboard to a computer an give various individual separate access, like with a remote login?
perhaps something like Concurrent Users Sessions
Unless you want to run Linux and really know your way around the terminal, x-window session and whatever else is involved I would say this is not possible.
Neither Windows nor Mac OS X are able to fully operate multiple user sessions simultaneously using a single computer.
For Mac OS X it requires the main machine running 10.7 Lion and each user you want to operate on it requires another Mac to access the session remotely. This (new) function is called "multi-user screen sharing" or "virtual display".
On Windows it is called Remote Desktop Services (former Terminal Services). It requires a full server installation and licencing and each user who wants to access a session requires at least a Thin-Client that is RDP capable.