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 a bunch of other keyservers not part of the SKS pool (listed below the same status page) detected at the synchronization of the peers.
The default keyserver for GnuPG, keys.gnupg.net:11371, now points to the SKS pool, meaning that when you are visiting that GnuPG keyserver it redirects you to one of the server of 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.