These things do seem to have a bad habit of sneaking up on you. With me it was "Melodrama, angels, bla bla, girl-of-the-week dead, what else is new - hey, wait a minute!"

Estelle - Jack's girlfriend that he left during the war. And then reconnected with pretending to be his own son. o.O
Jenny - Martha's Human Nature sidekick.
The Genius - the gal who got shot compliments of John "Poodleshagger" Hart, and then tried to blow him up from beyond the grave. (Too bad it didn't work.)
Lizzie - fuck, I can't even remember. Oh yeah, she was the rape victim from Ghost Machine.
Marie Thomas - the ex-HIV patient eaten alive by alien bugs.
Mary - Toshiko's lesbian alien sex adventure. 'nuf said.
Sally Phelan - the bride-to-be converted to a Cyber(wo)man, and zapped by the totally AWESOME Mrs. Moore.
Stacy Campbell - plumpy going to dump her boyfriend, gotten turned into a small horde of walking alien fat-babies.

(Dear lord. It appears I rather love making lists today.)