Stitch UV maps in Blender

To stitch separated UV islands do the following
Go into Edit Mode, and make sure Face Select Mode is enabled
Press (A) to view all UV island
In this example, I have two separated UV island and several loose faces
Press (Alt + A) to deselect everything
Then Press (L) to select only the Linked Faces of a UV island
Make sure Seam Select is enabled, the Seam Select limits the selection to Seams.
(Shift + Select) the face you want to stitch to the UV island
Go into the UV Image Editor, and make sure Edge Select Mode is enabled
Select the Edge which is the border between the UV island and the loose face
Press (V) to stitch
The edge now will light up green
Press (Enter) to apply the stitch
The loose Face will get moved and stitched to the UV island.