I really don't think there is anything remotely as good as Training Peaks WKO+ but it does cost a bit, but not as much as, say, one night in a B&B....
Hunter Allen is the guru of Power, maybe, and his book is the ONLY one I know of that tells you how to train with Power...
It can also work with heart rate, but you have to estimate the TSS (Training Stress Score) of each ride, for it to work best..