I’ve recently retired from active consulting, and am in the process of renovating this website.
If you want to improve your hardware or mixed hardware/software product development, I strongly recommend Katherine Radeka and her colleagues at Rapid Learning Cycles.
I’ve worked extensively with them over the years and they have some great training products as well as individualized consulting.
For pure software development, you can’t go wrong with Johanna Rothman. Her books on product development and management are gold mines of useful techniques and insights.