Sankhara (mental fashionings)
Viññana (consciousness)http://www.accesstoinsight.org/index-su ... ml#khandha
Rupa all that say do not have any feeling. In Abhidhammattha Sangaha, there are 28 rupa. All (material and some non-material) are all in this rupa. As a human-being max. rupa we have will be 27 (male or female characteristics, every few will have both)
Vedana - feeling if say Vedana 3, would be happy (good), misery (bad), and indifference. Vedana 5 will be 1. mental feeling good (happy) 2. physical happy (pleasure) 3. indifference 4. mental feeling bad (unhappy) 5. physically unhappy. Just breaking feeling into mental and physical aspect.
Perception simply say like this whenever we see, hear, smell, taste, touch (feeling physically) and we realize, know what they are. It's perception. We have must Perception to be able to know what we see, hear, smell, taste, touch before going to the process of knowing through mind. Kind of memory in the object or non-object.
Viññana (consciousness) can be understood like that of soul.
Sankara - in all there are 52 mental formation (52 types of cetasika. But Vedana and Perception are also cetasika, thus Sankara is the remaining (50 cetasika). As some have already mentioned earlier, Sankara is the one that form or shape Conciousness Vinnana (mind, soul etc.) to be good or bad.