Jumpcut is a free application for OSX that simply buffers everything you copy/cut into the clipboard. This buffer is accessible as your clipboard’s history through an icon on your menu bar:
or through a pop-up bezel:
that can be triggered with a hot key:
By default it can go back to the last 40 entries, though this is configurable through the Preferences.
That’s all there is to it! It’s does what it says very simply and intuitively and works very well. I’ll admit that for the first few days I would keep forgetting that I now have a running history of my clipboard but now I can’t imagine not having it available.
Recommended.