In the Cloud Broker Portal on the External Networks page you get an overview of the number of available ("free") IP addresses per external network:
From there you can click through to the External Network Details page:
Under the section Free IPs all free IP addresses are listed:
Next all cloud spaces are listed that use one of the external network IP addresses :
Also all virtual machines are listed that are directly connected to one of the external network IP addresses.
See External Networks for more details.