Just 'borrowed' this list from Yahoo answers:
Red haired Super Heroes and Villains:
Phoenix from X-Men (Jean Grey aka Black Queen)
Goblin Queen (villain from X-Men, Jean Grey's clone)
Phoenix II from X-Men (Jean Grey's daughter from alt. future)
Mystique from X-Men (her hair can be any color, but most of the time in the comics it's a dark red I think)
Black Widow from Avengers
Scarlet Witch from Avengers (might be brown hair, not sure)
Firestar (from X-Men + Avengers)
Medusa from Inhumans
Crystal from Avengers / Inhumans (sort of orange hair)
Tigra from Avengers (again, sort of orange)
Hellcat from Avengers / Defenders
Wolfsbane from New Mutants / X-Force
Vindicator (Guardian II) from Alpha Flight
Red Sonja
Mary Jane Watson
Poison Ivy (as you mentioned)
Batgirl (Barbara Gordon, 1st Batgirl)
Batwoman (the new one)
Hawkgirl (sort of orange, i think)
Starfire from Teen Titans
Mara Jade (from Star Wars novels, Luke Skywalker's wife)
Dawn (indie comic by Joe Linsner)
Ariel from "Little Mermaid"
Anna Mercury
7 of 9 from "Star Trek: Deep Space Nine"
Jessica Rabbit from "Who Framed Roger Rabbit"
Daphne from "Scooby-Doo"