Inspired once again by nicu’s post about his orb research i have decided to write a simple tutorial on how to make a basic bubble (bubble, orb, ball, whatever you want to call it.)
This Tutorial uses the blur filter that is only in Inkscape version 0.45 and later.
Step One
Open Inkscape and draw a circle.

click for the full image
Step Two
  1. Set the Fill colour of the circle to None
  2. Set the Stroke colour of the circle to the colour that you want, I chose blue.
  3. Make the stroke width nice and thick.
  4. Play with the blur amount in the fill/stroke dialog to blur the circle up a bit.
This is how it should look:
Step Three
  1. Now, take the circle tool and draw an ellipse towards the top of the original circle.
  2. Set the ellipse fill colour to the same colour as the blurred outline circle
  3. Set the ellipse stroke colour to none
    4. This is how it should look:
  4. Now, change the fill of the ellipse so it is a gradient from the colour you chose before to transparent
Step Four
  1. Now, Duplicate the outer blurred circle object (Right Click on the circle and choose duplicate)
  2. Set the blur of the newly duplicated circle to none
  3. Make sure the unblurred version of the circle is on top of everything.
  4. Press Control+A to select all the items
  5. In the menus up the top choose Object > Clip > Set
Step Five
  • Add a little light spot on your bubble and blur it up a bit, and you’re done!