Quicksilver plug-ins can add some cool functionality. One great one is the Clipboard History plug-in. Install it from the plug-ins page (which also allows you to set the history size via the plug-in's propteries). Then, when you invoke Quicksilver, hit APPLE-L to get to your clipboard history list. From this clipboard history list, you can paste by either using the arrow keys or using the number that shows up in the left-hand column.
One of the tips in The Productive Programmer is to use clipboard history tools so that you can start copy and pasting in batches, rather than the wrist-achingly inefficient copy-switch-paste-switch-copy-switch-paste operation most people do.
Quicksilver: just your type