The problem with IES materials is there are so many possible IES files you can choose from that it would be hard to even begin to build a collection that would be moderately comprehensive.
That said, here is a small sample set of Erco IES MXM files -- these are made from the sample IES files that come shipped with the Maxwell Render Suite... they really have no purpose other than to show how Maxwell handles IES files.
Obviously the more ideal solution is to have the embedded emitter character type support IES file linking so you can use whatever IES file from whichever lighting manufacturer you need to work with for your particular project... hopefully this will be feasible to do.
Make sure to apply these to a small sphere or your results may not look right.
Edit: I guess you'd need the IES files too 
http://dl.dropbox.com/u/41250852/ies.zip
These ies files will need to reside at C:\Program Files\Next Limit\Maxwell 2\ies*collection name* therefor I'm not sure the MXM's will work on a mac.
Best,
Jason.





