Yeah for some bizarre reason Workbench has the Clipboard/ in Ram Disk: but most of the programs won't let you highlight text to copy & paste!
I'm not entirely sure what King-Con does but I use it and it makes the Shell much nicer, adding a scrollbar and buffer. MCX is very nice and recently I've set my middle mouse button to cycle screens, which is incredibly useful. Rather than press 'Left-A m' you can just click and hey presto. Good too for games that don't have a screen swapping button and you're too lazy to do the key combo.
;-)