ClipboardWatcher is intended to be a one-trick-pony, though like many applications I am sure it will grow into a bloated beast. It's one trick is this. It sits in the background and watches the clipboard for changes, if there is a new text item it will append the plain text (along with some optional information: timestamp and frontmost application name) to a text file of your choice.
I installed this on Mac OS 10.4.9. My preference changes wouldn't stick - I kept trying to change the name of the file that the clips are stored in, and it kept changing the name back to the default. I also turned off the debug option, but all my clips appeared in a debug window. Defintely alpha software. Check back when it's gone up a few versions!