Yes, as Russell says plenty of distribution transformers use aluminium. 

However, as far as I know most low power transformers use copper windings still. I had a quick search on Farnell, Mouser, etc, and could not find any aluminium wound transformers or aluminium magnet wire.        

As long as it's properties are taken into account though then there should be very little or no difference in performance for any application, apart from an aluminium transformer of the same rating might be a bit bigger. I would think any concerns would be more to do with things like ensuring reliable Cu/Al joints and different mechanical properties (expansion coefficient, embrittlement of Al, etc) rather than performance.

You can even get [silver wound][1] transformers too, popular in high end audio gear along with things like oxygen free cables and [gold wiring][2].  


  [1]: http://www.hificollective.co.uk/components/trans_output.html
  [2]: http://www.thejadeaudio.com/Products.html