House in House (Tokyo, Japan), by MAMM Design
Source: http://www.mamm-design.com/?p=78
Gregory Han's Black Hole Home Office
Source: http://www.apartmenttherapy.com/the-black-hole-closet-home-off-123312
OfficePod
These small prefabricated pods are ready-made, self-contained home offices that can be installed wherever there's space.
Source: http://www.officepod.co.uk/gallery/
Old bus office
This home office was created using half the front end of a broken down bus. Check out the link for more pictures.
Source: http://www.reddit.com/r/pics/comments/y267n/bus_office/
Collector's loft (New York, USA), by UNStudio
Source: http://www.mybestluxe.com/luxe-tendance/loft-galerie-a-new-york-by-unstudio/
Marrickville House (Sydney) by David Boyle Architect
Source: http://www.davidboylearchitect.com.au/projects/marrickville-house-1-2/
The Hackney Shed (Hackney, UK), By Office Sian Architects
Source: http://www.officesian.com/projects/hackney.html
Alwyne Place (London, UK), by Lipton Plant Architects
Source: http://www.lparchitects.co.uk/alwyneplace