The Marquee tool just doesn't get any respect.

Most folks figure out how to use the Marquee tool pretty quickly.  Just click on the tool.  Click on a starting point in your image, and drag.

However, with a little ingenuity, the Marquee tool can be used to make fairly complex selections.  And it can make them easily and quickly.  For me, at any rate, in many cases, this little trick is simpler and faster than using one of the lasso tools.

Open your image.  Click on the Marquee Tool.  If the Rectangular Marquee icon is displayed, click on the tiny arrow, and choose Elliptical Marquee from the sub-menu.

Next:  And this part is the key to the whole trick:  Look up at the Options Bar  See the icon with two little blues squares? That icon indicates "Add to Selection".  Click it.  (The next icon with the white square overlapping the blue square indicates subtract from selection -- don't click that one, not yet.)

Click a starting point on the object you want to select.  Drag to form the Marquee's oval shape.  Don't try to select the whole object.

Click another starting point, drag another oval.  Overlap your first oval.  Click another starting point, drag a third oval overlapping the first or second. 

As long as the Add to Selection icon is active, each overlapping oval is added to the selected area as soon as you release the mouse button.

You'll be surprised at how quickly you can do this.  Click starting point, drag overlapping oval, release mouse button.  Repeat.

Oops.  I went too far past the edge.  To remove an area from the selection, click the Subtract from Selection icon.

Click a starting point at the edge of the object, drag the oval away from the object, release the mouse button.  Repeat until you've moved the selection line back where you want it.

Okay.  That actually only took a few minutes.  Now that I've manged to select an airbourne Police car, what shall I do with it?

To apply some special effect to the background, I'll need to "inverse" the selection.  Right now the Police car is selected.  I want to tell PSE to select everything except the Police car.  Click Select -> Inverse

I'll try a Motion Blur.  Click Filter -> Blur -> Motion Blur.

Experiment with the Angle pointer, and the Distance slider, until you see an effect you like.

To remove the "marching ants" of the selection line, click Select -> Deselect.

What can't you do with the Marquee tool?  Select a diagonal line.   But there are several other tools in the tool box to deal with that!

More on Photoshop Elements Selection Tools:

Being Selective: Photoshop Elements Selection Tools

Photoshop Elements Selection Tools: The Marquee Can Do More Than You Think

Photoshop Elements Selection Tools: The Magic Wand

Photoshop Elements: Fast And Easy Blue Skies