In QGIS 1.8 (Lisboa)

(No plugins required as it is standard)

Vector>Geometry Tools> Multipart to singleparts

This will create individual polygons to single polygons.

In QGIS 1.8 (Lisboa)

(No plugins required as it is standard)

Vector>Geometry Tools> Multipart to singleparts

This will create individual polygons from multipart polygons.