Is there a 3-dimensional airspace viewer?
You can download Google Earth airspace files for most countries, and move through them in 3D to explore what they would look like for various areas.  For example, you could see where you would be "under" a Class B shelf, or where you might navigate to avoid B/C/D airspace and "surface airport E airspace" (if you're flying an ultralight, for example). 

These files can be downloaded from 3dairspace.org.uk

Here is a screenshot I just captured of the Seattle Class B, looking northwest from the southeast corner.