Also, how to display both scalebar in kilometers and both lat/long degrees and northings/eastings in QGIS 1.8 Composer? Layer is projected to UTM. Thank you.
In essence QGis uses the CRS of your project for both the scale bar and the grid.
To show a secondary grid look at this link
for the scale bar I do not know...
Hope it helps
Lat/lon 'grids' are usually called 'graticules'. I think the method for creating a lat/lon graticule as described in this document is sound. However, I think that the resulting shapefile needs further processing to make it plot properly on a projected map (UTM for example) such as yours.
After creating the graticule the lines should be densified to add extra vertices to them: Vector -> Geometry Tools -> Densify geometries. I used a value of 100 to produce the graticule shown as blue broken lines in the picture. The extra vertices in the lines 'pegs them to the ground' at more frequent intervals. Before densifying each line was defined by just two vertices, one at each end, and would plot as a straight line on a projected map, which it shouldn't. You can see the errors that arose with the graticule shown on the map in the document. Apparent errors I should say, I'm open to correction if I'm wrong about this.