Well, there is the problem of where to look. There is a pretty
comprehensive list of the delegation status of blocks at the
/8 level that is pretty accurate. I suspect that the RIRs can
provide pretty good detail for the recent (1996 and later) delegations.
The historical delegations are -much- harder to track. I've been
spending some time on clearing up detail on older /8 blocks
and this data may make it into the publicly visable registries
if they want it. 128.0.0.0/8 is done and I've got most of
192.0.0.0/8 complete.
-- bill