Can anyone recommend any opportunities for IT professionals to develop their relationship management skills, such as negotiation, managing expectations, time management, etc. These could be workshops, books, websites, etc.

Iomapr-

I have worked for tech companies for the past 3 years. We offer the same soft skills training for our IT people as we offer our sales or client services people. We want the training o be cosnistent across teams and ensure that managers across the organization are speaking the same language and using the same techniques.
I would be happy to recommend some of the vendors I have used in the past if you like.

That would be great if you could recommend the vendors. It makes sense to offer the same type of training since many of the factors that make up a successful client relationship are very similar.