There is a distinct advantage in basing reparations on slavery in that (1) slavery can be fairly precisely defined and its worth (as lost wages) evaluated, whereas segregation and discrimination cannot; (2) there are surviving parties who can be held legally responsible for slavery, to wit, the United States government and the governments of the several states which supported slavery prior to the Civil War (all or most of those then in existence), whereas much of segregation and discrimination was (and is) carried out privately by persons who are now dead.
Doing some very informal calculating several years ago, I arrived at a figure of six trillion dollars, or about $200,000 per capita if there are 30,000,000 full heirs of the slaves. Of course this figure could be much higher or lower depending on how one calculated; I proceeded rather conservatively. Note that _only_ lost wages are considered; other charges, as for pain and suffering, are excluded because it is much harder to put a money value on them. Because the assertion of debt is so controversial, it is well to construct an armor-plated argument. Even discussing the amount, regardless of whether anything is ever paid, would be of enormous educational value.
Arguments such as that the slaves received goods and services or that they were better off than in Africa are of no account in this approach, because we are discussing only wages owed. Since the slaves were slaves, they could not make contracts to receive the goods and services, and so these were gifts or impositions rather than compensation.
I thought that the proposal for payment should specify that the money be paid by the governments mentioned out of general revenues, probably _per_stirpes_ -- that is, a person's share of the money would depend on the proportion of a person's ancestors who could reasonably be identified as having been slaves. This would account for persons of less than full ancestry in slavery. In any case the money _must_ be paid to individuals to prevent it from being skimmed, diverted and dissipated by politicians, bureaucrats, and institutional functionaries into "programs".
I believe all of the above is thoroughly within classical liberal political philosophy, so that no charge of communism, socialism, social democracy, Welfarism, or improper reification of abstract categories could be brought against it -- neither group responsibility nor group benefit is suggested. It is simply the payment of an undoubted debt to those who are undoubtedly owed the debt by those who undoubtedly owe them. It is also theoretically feasible in the sense that, while six trillion dollars is a lot of money, it _could_ be raised by the governments. For instance, the Federal government could abolish the Department of Defense at $300 billion a year and pay off the six trillion in just 20 years, plus a bit of interest. In test runs on Usenet, my proposal caused great frothings at the mouth, but no substantial counter-arguments.
But perhaps all of this is redundant in these environs.