There are a number of Oracle packages related to networking. The UTL_HTTP and UTL_TCP packages allow you to access the internet through SQL and PL/SQL. The UTL_MAIL and UTL_SMTP packages allow you to interact using email. Because of the security risks related to network access, a package called DBMS_NETWORK_ACL_ADMIN is available in 11g which is related to "Access Control Lists" which limit the network resources available to database users.
Numerous other packages have networking implications including UTL_URL which is used to manipulate URLs and various packages related to XML processing.