I don't believe it is SPAM to send an e-mail message to potential partners using the contact information they list on their own websites.
Abuse is bad and getting worse.
Having said that, it would seem like common sense that it would be okay to send a single e-mail to a business that you want to do business with. The key to e-mail is integrity and a personal touch. If you respect the recipient, he is more likely to respect you. Build your online business on the basis of a good reputation rather than in a manner that causes recipients to react negatively against you and vow never to do business with you. Lack of integrity has given commercial e-mail a very bad name.