I was browsing around the most recent release of Golden Cheetah and found reference to Cycling Analytics. Upon trying it out I find that its exactly what I've been looking for to plan and track my training. Up till now I was using Rubitrack, Strava & Golden Cheetah. None of these offered the ability to plan training and predict fitness/freshness ala Training Peaks (which I would not pay for). There is a monthly charge for Cycling analytics (about $9. USD a month) but this is a lot less than Training Peaks and I like the interface more. Theres a free 30 day trial. Full Disclosure: I never heard of Cycling Analytics before this month and have no connections with them beside really enjoying this product :-)
https://www.cyclinganalytics.com