Yesterday we got a question from a customer whether is was possible to have versioning on a library, and at the same time disabling the check in/ check out option. I didn't know, but after a view minutes of looking around, my colleague Casper found the settings in the document library settings under Versioning Settings.
You can actually configure a couple of interesting settings on this page.
Require content approval for submitted items? This is a setting you will especially use on development environments to prevent having to approve every change in for instance a master page or a page layout.
Create a version each time you edit a file in this document library? Here you can choose between no versioning at all, just major version and minor and major versions. You can also limit the number of versions to retain.
Who should see draft items in this document library? This setting is especially usefull in live environments with sensitive data.
Require documents to be checked out before they can be edited? So you can actually turn off the check in/ check out feature. Something I would advice against, because it would bring you back to the SharePoint 2003 functionality where it is possible to work in the same document at the same time with several people and thus when the second person saves his or her changes overwriting the changes the first person made.