ClipMate is very good. It is commercial, starting at $34.95. Its basically a database of your clipboard. By default it puts items in an Inbox and you can create further folders to file items in. There is a hotkey to the main window and you can assign shortcuts to individual items so you can quickly paste them. Also, you can search your clips and even write SQL to find stuff since it is running off DBISAM database.
There is a 30 day trial available, but the software seems to still be usable after the time limit has lapsed. There is also a Portable Apps version you can run off a pen drive, which I've found very handy.
I tend to use it for writing documentation and do screen captures as I'm installing apps and store various bits of related text, which I can then refer to later.