When viewing a Stack in Fan or Grid modes, you can manipulate the icons via drag-and-drop and invoke Quick Look by typing a space while hovering over the icon. However, these actions are not supported in the standard List View.
OS X 10.7 (and possibly earlier versions) supports a 'new list view' in which icons can be manipulated in the same ways as in the fan and grid views. It can be enabled via the Terminal command:
defaults write com.apple.dock use-new-list-stack -bool YES && killall Dock
Also, when the New List View is in effect, icons sizes can be changed with the Command+Plus and Command+Minus key combinations.
To return to the default list view use:
defaults write com.apple.dock use-new-list-stack -bool NO && killall Dock
[crarko adds: This worked for me in 10.6.8 as well.]