CCleaner is one of the best software to optimize a system. I am using this on my mobile for some time it is working excellent. Just one touch is required to analyzes the memory of the mobile and it shows the results readily about the the space that can be saved.
Very useful for the mobiles which have low internal storage as cache memory can be erased very easily using this. One more feature, if added, will be very good is the result should also show active applications and can be chosen which we want to close.