Domainindex.com published some research about the oldest 100 domain names and came up with some pretty interesting stats.

58 are now owned by a different entity from the one that registered it
35 are owned by Fortune 500 companies
7 are owned by pioneers of the web
12 Do not resolve
4 are Parked
84 are in use 

These companies hold more than one of the oldest 100 domains:

3 Oracle
3 Verizon
2 Northrop Gruman
2 Intel
2 Siemens
2 AMD
2 Raytheon

These domains do not resolve or are not in use

unipress.com
grebyn.com
gmr.com
rdl.com
ub.com
gte.com
mentat.com
tti.com
kai.com
ray.com
kccs.com
nsc.com

These are parked

quad.com
ide.com
prime.com
mcc.com

These Domains look like being owned by domainers

symbolics.com
prime.com
datacube.com
spdcc.com
cayman.com
kccs.com
ide.com
octopus.com
mcc.com
ub.com
kesmai.com

These are active and belong to Fortune 500 companies or large entities

xerox.com
sri.com
data-io.com
hp.com
ibm.com
intel.com
ti.com
att.com
tek.com
fmc.com
ge.com
boeing.com
siemens.com
fluke.com
mentor.com
nec.com
adobe.com
cisco.com
amd.com
philips.com
dupont.com
lockheed.com
ncr.com
alcoa.com
ccur.com
convergent.com
unisys.com
cgi.com
apple.com
slb.com
utc.com
trw.com
gene.com
dsc.com

These domains still belong to pioneers of the WWW, the same people that registered them<

cfg.com
tic.com
nma.com
entity.com
vortex.com
itcorp.com

1 was subject to a UDRP (octopus.com)

DomainIndex.com also published a list of all the companies that used to own one of the 100 oldest domains that are out of business which you can see on the full post.