The next gen of capacitors now appearing in RC are: "Super Caps"
Super Caps use an electrical "double layer" where the dialectric is only nanometers thick. This allows two main advatages: The ESR is extremely low due to the physical proximity of the anode and cathode, AND the capacitance (uF) is many many times higher than a comprable sized standard cap due to it's far more tightly coiled components.
Super Caps have one more big RC advantage - they are "flat" shaped, instead of "can" shaped. So you get more uF, lower ESR, and get it in a smaller and more easily managed package.
***Shameless plug alert***
We're bringing in Super Caps from Speed Passion in our next order
And of course all this coolness comes at a higher price than standard caps...