Made in Blender 2.62.
The composition of each orb is as follows:
Particle emitting icosphere core.
Turbulence field.
Icosphere shell with collision settings and a solidify modifier.
The floor is a stock image imported as a plane with low-gloss reflections applied.
The sky is a brightened city stock image with heavy bokeh applied, mapped to the Blender sky.
Inspired by Andrew Kramer's "Glass Orbs" tutorial on Video Copilot.