Often, I'm asked by business owners about management resources to help them. Many entrepreneurs didn't make it to the C-level executive position before becoming entrepreneurs so they lack some of the managerial experience gleaned along the way.
This is a really impressive site, full of incredibly powerful information. Although it may be designed for corporate managers, its information is no less pertinent to the entrepreneur who needs to quickly learn how to develop their management skills.
http://www.managementhelp.org/