Both SKS Keyserver Pool (stats) and PGP Global Directory are online.
I usually use sks-keyservers, since it consists of many servers which synchronize their databased continuously, while Global Directory is a single, commercially operated server.
There also exist pgp.mit.edu (stats) aka cryptonomicon.mit.edu (not part of SKS pool, but does sync with other servers)
and keys.gnupg.net pool (stats) (the default keyserver for GnuPG).
Edit: keys.gnupg.net is now an alias for the SKS pool
If your email address is at a domain name you manage (i.e. can have arbitrary DNS records created), it is also possible to publish your PGP key using DNS. The easiest method for that is PKA, which only requires the ability to create TXT records; see the article on publishing PGP Keys in the DNS.
PKA, as well as two other methods (CERT and IPGP CERT), are described in this guide in much more detail.
One downside of all three methods is that GnuPG must be manually configured to use them, and PGP.com doesn't even support using DNS. Meanwhile, practically all versions of PGP and GnuPG can use keyservers.