If you'd like the key they used to sign RPMs with, I copied it below. I got it from this Fedora forums posting and also using wayback on http://gd.tuwien.ac.at/infosys/phone/skype/rpm-public-key.asc which I saw mentioned a few places.
The key by itself is worthless if the skype isn't actually signing their RPMs which is indeed the case. The gpg check is complaining because the RPM isn't signed, not because you don't have the key.
If you run rpm -K some.rpm you can check to see if an RPM is signed. Notice in the output in the command below, the skype RPM does does not list 'gpg' anywhere whereas the signed 'at' RPM from CentOS does and the signed 'aspell' from Scientific Linux does. You can run rpm -Kv some.rpm if you want more verbose output. The RPM website has more info on signing RPMs and how to tell if they're signed if you're interested.
$ rpm -K skype-2.1.0.81-fc.i586.rpm
skype-2.1.0.81-fc.i586.rpm: sha1 md5 OK
$
# This is a CentOS RPM that I have already imported the key for.
$ rpm -K at-3.1.10-43.el6.i686.rpm
at-3.1.10-43.el6.i686.rpm: rsa sha1 (md5) pgp md5 OK
$
# This is a Scientific Linux RPM that I do not have a key for.
# It complains I don't have it but still shows the RPM as being signed.
$ rpm -K aspell-0.60.6-12.el6.i686.rpm
aspell-0.60.6-12.el6.i686.rpm: (SHA1) DSA sha1 md5 (GPG) NOT OK (MISSING KEYS: GPG#192a7d7d)
$
In summary, the problem you have isn't that you can't get their GPG key, it's that they don't sign their RPMs. You're going to have to go without the gpgcheck to get skype installed.
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1.2.4 (GNU/Linux)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=Up0v
-----END PGP PUBLIC KEY BLOCK-----