In QGIS 1.8 this type of diagrams is only provided by the "diagram overlay plugin" (See Plugins => Manage Plugins). Once enabled you have in the vector layer properties a new Tab "Overlay" which offers "Bar Chart" in the dropdown.
QGIS 1.9 / 2.0
With QGIS master (soon to be 2.0) it is possible to draw piecharts, histograms and text diagrams with the builtin diagram engine (the diagram overlay plugin has been removed, as it is superseded by this)
In the vector layer properties => Diagrams you can choose "histogram" as type.
Unfortunately, with neither of these it is possible to draw "double" bar diagrams.