  Collisionless, cold dark matter in the form of weakly-interacting massive
particles (WIMPs) is well-motivated in particle physics, naturally yields the
observed relic density, and successfully explains structure formation on large
scales. On small scales, however, it predicts too much power, leading to cuspy
halos, dense cores, and large numbers of subhalos, in apparent conflict with
observations. We consider superWIMP dark matter, produced with large velocity
in late decays at times 10^5 s - 10^8 s. As analyzed by Kaplinghat in a more
general setting, we find that superWIMPs have sufficiently large free-streaming
lengths and low phase space densities to help resolve small scale structure
problems while preserving all of the above-mentioned WIMP virtues.
