  We show (analytically and by numerical simulation) that the zero-temperature
limit of the distribution of the thermopower S of a one-dimensional disordered
wire in the localized regime is a Lorentzian, with a disorder-independent width
of 4 pi^3 k_B^2 T/3e\Delta (where T is the temperature and \Delta the mean
level spacing). Upon raising the temperature the distribution crosses over to
an exponential form exp(-2|S|eT/\Delta). We also consider the case of a chaotic
quantum dot with two single-channel ballistic point contacts. The distribution
of S then has a cusp at S=0 and a tail |S|^{-1-\beta} log|S| for large S (with
\beta=1,2 depending on the presence or absence of time-reversal symmetry).
