From Fedora Project Wiki
Note that yum list will list installed and not installed packages:
[jjmcd@Conor ~]$ yum list apr* Loaded plugins: refresh-packagekit Installed Packages apr.i386 1.3.3-1.fc10 installed apr-util.i386 1.3.4-1.fc10 installed Available Packages apr-api-docs.noarch 1.3.3-1.fc10 fedora apr-devel.i386 1.3.3-1.fc10 fedora apr-util-devel.i386 1.3.4-1.fc10 fedora apr-util-freetds.i386 1.3.4-1.fc10 fedora apr-util-ldap.i386 1.3.4-1.fc10 fedora apr-util-mysql.i386 1.3.4-1.fc10 fedora apr-util-odbc.i386 1.3.4-1.fc10 fedora apr-util-pgsql.i386 1.3.4-1.fc10 fedora apr-util-sqlite.i386 1.3.4-1.fc10 fedora apricots.i386 0.2.6-2.fc10 fedora aprsd.i386 2.2.5-15.5.fc10 fedora
and give you a chance to limit the list.