Due to other pressing obligations, I haven't been following this matter carefully, but Peter Momtchiloff calls my attention to an interesting chart from The Guardian; here are the four provinces with the most, shall we say, "suspect" results:

East Azerbaijan: Ahmadinejad received 10% in 2005, ‘57%’ in 2009.

Ardabil: Ahmadinejad received 7% in 2005, ‘51%’ in 2009.

Lorestan: Ahmadinejad received 9% in 2005, ‘71%’ in 2009.

Kuzestan: Ahmadinejad received 16% in 2005, ‘65%’ in 2009.

Hmmm.

UPDATE:  A useful round-up of links to analyses here.