I'm excited to hear about your survey of Michigan Energy Businesses!  This is a FANTASTIC project.  I REALLY appreciate your initiative. 
 
I don't know where to start talking about this... so I'll just plunge in.
 
I love the letter/survey idea.  It could result in so many things... besides just good marketing info.  I.e. potential jobs, new ideas, friends, increased communication, lobbying power, learning for all!  The start of our energy network website!!!  A grant!  A job!
 
Here's my quick contribution to expanding the list... perhaps we can create a database and/or even get a grant to work on this!!!!  It is certainly a valuable exercise that could benefit many!!! 
 
Here's a nice list from GLREA:  http://www.glrea.org/bizMemCategories/
Here's a list of energy raters from RESNET:  http://www.natresnet.org/directory/rater_directory.asp#Search
 
Here's a regional recycling directory:  http://www.urbanoptions.org/resources/directories/recyclingDirectory.php
 
Energy Efficient Mortgage providers
http://www.michigan.gov/documents/CIS_EO_Inside_hers3_38747_7.htm
 
I started a group called MBEE (Michigan Businesses for Energy Efficiency) a few years ago.  It looks like it's now more of a directory:  http://urbanoptions.org/resources/guides/guideProdServMain.php
We put together some marketing materials for this initiative which may still be useful.
Here's another, older list of MBEE folk...http://www.msu.edu/~bahrieda/MBEE.htm
 
The list of co-sponsors for last year's energy conference is GOOD too...
http://www.glrea.org/education/UTP/2005_Michigan_Energy_Conference_Exhibitors.html
 
There is some great marketing material here:
http://www.glrea.org/education/UTP/2005_Michigan_Energy_Conference_Presentations.html but it's a little buried in the presentations.
 
The Energy Star Program has some GREAT marketing support materials:
http://www.energystar.gov/index.cfm?c=partners.pt_index
 
Michigan Independent Power Producers Association could be a tremendous ally...
http://www.mippa.net/web/   Hey!!! They're in HOLT (MIPPA: 845 S. Cedar St., Bldg. B, Ste. 100, Holt, MI  48842
 
Michigan Solar and Wind Suppliers (PDF)
http://www.michigan.gov/documents/CIS_EO_Inside_broch_solar_and_wind_67997_7.pdf
 
The Central Michigan Sustainable Business Forum is a very cool group that's starting up in our region...
http://www.cmsbf.org/memberlist.html 
 
Last but certainly not least is the "Michigan Sustainable Energy Coalition"
Good marketing material:  http://www.michigan.gov/documents/MSEC_Launch_ExecSumm_136865_7.pdf
 
Source of grants???  http://www.michigan.org/medc/21stcenturytour/overview/index.asp
 
The list of people I invited to speak include suggestions from our class, folks who've done a good job in the past, and or are in the area....
not necessarily energy businesses.  I'll be happy to share the list, but I'm being called to play frisbee at the moment!
 
Perhaps these names should be put on our little Energy Network Website????