+2  A: 

I haven't tried this for any of my own work, but perhaps the matplotlib AxesGrid toolkit might be what you are looking for.

Tim Whitcomb
A word of warning, at the moment AxesGrid is not in the stable release of matplotlib so you have to fetch from latest source. Did work though.
pufferfish
+2  A: 

Don't use subplot but axes to create your subplots - the latter allows arbitrary positioning of the subplot.

Jouni K. Seppänen