It really depends on what your goals are. I designed a Masters in Org. Leadership (which is mostly soft skills); I would have to know what you want to develop and then I can point you the right direction. That would be easy for me and I could do it quickly, but I can't point you to generic soft skills. It is like saying what is the best tasting ice cream without knowing what you like. It sounds like you are looking to improve, but targeting is going to be critical.Otherwise you will waste a lot of time.