I'm worried I'm missing something terribly obvious here: how do you set the alignment (left / centre / right) for feature labels? I'm referring to QGIS 1.8, and using the 'Label' toolbar, rather than Layer Properties labeling.
Go to the tab 'Data Defined Settings'. Scroll down to the bottom and the section marked 'Position'. Here you can define where the label will appear but you need attribute fields for this. Add a field to your attributes called (say) 'h_align'. Now set all its values to 'Right'. Now use this field as your Horizontal Alignment option (you must set X and Y coordinates first and you'll need attribute fields for those too).