In fact Torchwood, somewhat tiresomely, is being mentioned in every episode (just as "Bad Dog" -- I mean "Bad Wolf" was last year). The odd thing is that this means that Torchwood is an institute founded by Victoria in order to prepare for alien attack with the Doctor specifically marked out as a reference and potential antagonist. But if it's existed since the 19th century, what was it up to all those times Earth was being invaded in the 70s (Cybermen and Yeti both cleaned out contemporary London, for example). And to what extent does their portfolio conflict with/duplicate UNIT? (The indication in "Christmas Invasion" is that UNIT is a secret but official organization which coordinates government crisis response to an invasion, but Torchwood is secret and unofficial -- though taking orders from the PM! -- that can engage the aliens. The Torchwood weaponry in "CI" is said to be recent -- I wonder what they had before?)
Must be weird having big piles of continuity loose ends to tie up before your show even gets on the air!
Outpost Gallifrey has an update page for the spin-off series
here.
P.S. For those who don't know, "Torchwood" is an anagram of "Doctor Who". RTD loves pseudoclever stuff like that...