Signaling is an important topic in the study of asymmetric information in
economic settings. In particular, the transparency of information available to
a seller in an auction setting is a question of major interest. We introduce
the study of signaling when conducting a second price auction of a
probabilistic good whose actual instantiation is known to the auctioneer but
not to the bidders. This framework can be used to model impressions selling in
display advertising. We study the problem of computing a signaling scheme that
maximizes the auctioneer's revenue in a Bayesian setting.

We study auctions with additive valuations where agents have a limit on the
number of items they may receive. We refer to this setting as {\em capacitated
allocation games.} We seek truthful and envy free mechanisms that maximize the
social welfare. {\sl I.e.}, where agents have no incentive to lie and no agent
seeks to exchange outcomes with another. In 1983, Leonard showed that VCG with
Clarke Pivot payments (which is known to be truthful, individually rational,
and have no positive transfers), is also an envy free mechanism for the special
case of $n$ items and $n$ unit capacity agents.