The channel from the Western Wall area to the Pool of Siloam is not yet open to the public, but you can get a look inside with photos posted by the Israel Antiquities Authority. Three high-resolution images are currently available at this page (or try this direct link to the zip file).
You can also watch a 3-minute video posted by the Israel Antiquities Authority, with archaeologist Eli Shukrun showing off the results of seven years of his work.
