RealGM

I was looking online for a calendar of important CBA dates, like official start of free agency, deadline to renounce cap holds, etc...but couldn't find it all in one place, anyone here know if this exists in one resource?

I think you'll find what you're looking for in question #118 of Larry Coon's FAQ:

http://www.cbafaq.com/salarycap.htm#Q118