When The Avengers started in 1963, The Wasp was the only female of the five original members. All the original members left in 1965, but there was still only one female out of the nine-person team; the Scarlet Witch.
The strip has several recurring female characters, but after the Supreme Court declared male-only clubs unconstitutional, a series of strips dealt with the necessity of introducing a regular female character. ("Nothing's more 'male-only' than Bloom County! We've GOT to introduce a WOMAN!") Eventually, Ronald-Ann was created as a regular.
Even more directly addressed in Outland: In the strip, a woman asked why all the well-known animal characters in comics and animation are all male, and any female animal characters were just The Girlfriend. Opus announced that the strip was just about to hire the first major female animal character star to join the main cast, Hazel the Hedgehog. In a brilliant sequence that ran for weeks, she lampshaded why most animal characters are male. (Are we asking girls to identify with a "little pig-rodent"? Can she participate in a slapstick pie fight if depicting violence against females is taboo? Is she still her own distinct character if we have to put a bow on her head?)
Alison Bechdel's Dykes To Watch Out For was made as a response to the Smurfette principle (as discussed in The Indelible Alison Bechdel), to force male readers to identify with the female characters, as women often have to identify with male characters. Over the last several years, more male characters have appeared; one of the main characters, Sparrow, had a long-term relationship and a child with a man named Stuart. This may have also been her accommodating what has become to be known as The Bechdel Test in her own work.
When the Justice League of America started in 1960, Wonder Woman was the only female member of the seven founders. It took almost a decade before Black Canary became the second female member (and that was only after Wonder Woman had resigned; it would take several more years before there was more than one woman on the team).
In The League of Extraordinary Gentlemen, Mina Harker/Murray is the Smurfette in the otherwise all-male League, and chosen to be the League's leader. Alan Moore said he titled it "Gentlemen" to reflect the sexist tendencies of Victorian times.
In Scott Pilgrim, one of Ramona's 7 Evil Exes is actually a girl. Justified by the fact Ramona is mostly heterosexual and only became bisexual during her "phase", so it's actually a surprise the group even includes a girl to begin with.
Peyo (their creator) caught some flak by admitting Smurfette was not intended to be a real heroic character at all, describing her in mostly childish ways. Originally, the Smurfs were all male (or possibly asexual). One cartoon explained that smurfs did not reproduce the way most creatures did; a stork magically delivered them as infants on nights when there was a blue moon. Thus, gender was a moot point. Smurfette's Origin Story was shown in the Hanna-Barberacartoon show. She was created by Gargamel to disrupt the lives of the Smurfs. (However, in the conclusion of that origin story, she rescued them single-handedly.)
Later, another female Smurf, the younger and more tomboyish Sassette, was created by similar means as Smurfette, except "less clay" seems to equal "younger". She is usually accompanied by three boy smurfs of roughly the same "age", and the four are collectively reffered to as "Smurflings".
The penultimate season added Nanny Smurf, who confusingly seems to have been a natural female Smurf, from Papa Smurf and Grandpa Smurf's generation.
The second movie expands Smurfette's story, claiming that Smurfette was originally something called a "Naughty" before Papa Smurf's spell, created as a Distaff Counterpart of Smurfs in general (not truly evil, but incredibly mischievous). In the actual movie, Gargamel creates two more of these creatures named Vexy and Hackus - one male, one female - in order to discover how to use Papa Smurf's spell to turn them into true Smurfs. Gargamel's actual goal is to use a device to extract "smurf essence" from not only the real Smurfs, but from Vexy and Hackus as well once the spell is cast, considering them Unwitting Pawns. The two eventually turn against him and are taken in by the actual Smurfs.
The newspaper comic Tumbleweeds had two Smurfettes — Hildegarde Hamhocker among the townsfolk of Grimy Gulch, and Little Flower among the Poohawks. Aside from Hildegarde's little niece Echo, other female characters are extremely rare (if not non-existent) in the strip.
Silk Spectre II from Watchmen is the only female super-hero of the second generation, while the WWII era group originally had two female members (Silk Spectre I and The Silhouette), but the latter was kicked out when it became known she was a lesbian. (As at least two males were known among the same group to be closeted homosexuals, the commentary on sexism is definitely intentional.)
When the "New X-Men" started in 1975, Storm was the only female member. Since Chris Claremont was writing, she wasn't alone for long.
Eventually, the X-Men became quite possibly the heaviest aversion of this trope in the entire genre. At some points in their history, female characters actually outnumbered the males.
The original incarnation of the Brotherhood of Evil Mutants had Scarlet Witch as its only female member.
Invoked in Youngblood: Judgment Day, where Glory is keen to the idea of re-forming the Allies of Justice because she enjoys being the only woman in a team of men — it's implied that it makes her feel like she's the one in charge.