Lesson:Lasso Tool
From Wikiversity
The lasso tools work in a way very similar to the Marquee Tool, the difference being that the lasso tool allows you to select free-form shapes.
[edit] The Tool
When you get into the higher level photoshoping techniques, you will often need a more detailed selection edge. For this the Lasso Tool is more suited. First, click on the lasso tool 
and scroll over your canvas. Then click and hold the mouse, and trace what you wish to select. That area will be selected when you let go of you mouse. In almost all ways other then shape it is identical to the Marquee tool. Variations include the Polygonal lasso tool, which you use by selecting points and the area between then will make up the selection edge, and the magnetic lasso tool, which is a sort of "AI" lasso tool.
