Opening attribute table using PyQgis?

Yes you can, at least with the latest master version and 1.8. It is a method exposed via iface

// C++ (signature)
void showAttributeTable (QgsVectorLayer *l)

# PyQGIS (example)
iface.showAttributeTable(iface.activeLayer())

You will need a preexisting reference to a QgsVectorLayer.

For direct editing of features it is also a method exposed via iface:

// C++ (signature)
bool openFeatureForm (QgsVectorLayer *l, QgsFeature &f, bool updateFeatureOnly=false)

# PyQGIS (example)
iface.openFeatureForm(iface.activeLayer(), feature, False)

You will need a preexisting reference to a QgsVectorLayer and a QgsFeature in both cases. The feature form opened and whether it is editable are dependent upon app settings and whether the feature's layer is in edit mode.