Rip and Teri: The 'Betty' is Teri, a meek and somewhat nerdy English teacher. The 'Veronica' is Tatyana, a glamourous and gorgeous ex-super spy and TV station CEO. However, while Tatyana thinks that the hero still has a thing for her, he's actually madly in love with Teri. It kind of helps that, in their brief romance, Tatyana manipulated and betrayed him, however.
Cindy (Betty) and Dusk (Veronica) in Faux Pas. As far as Randy (Archie) is concerned, the kind and straightforward Cindy has already won, but sly Dusk won't let the issue drop.
College Roomies from Hell!!!: While Dave seems to have chosen Veronica (rich-girl-with-issues Blue) over Betty (survivalist-psycho-chick Margaret), Dave remains close to (and admittedly emotionally attached to) Margaret.
Oddly enough, Margaret, the so-called Betty, was the one that barely knew Dave existed at the start of the comic, whereas Blue, the Veronica, was in love with him off the bat.
MegaTokyo: Piro (Archie)'s current girlfriend, Kimiko, is an emotionally insecure struggling actress (Betty), whereas Miho, his ex, is a very dark and enigmatic Veronica.
Inversely, Erika's former fiance was a close friend from high school (Betty), while her current beau, an insane American hacker genius / zombie slayer, is most certainly the male equivalent of the Veronica.
In Scary Go Round, sensible Erin Winters (Betty) and Perky Goth Dark Esther (Veronica) competed for The Boy's affection. Esther won.
A more recent love triangle involves Esther's friend Sarah, with Ryan Beckwith as the independent, older Veronica. Carrot would be a safer Betty here if his chances of success weren't those of the Isle of Wight trying to invade China.
Girl Genius has Klaus as Veronica, Bill as Betty and Lucrezia Mongfish as Archie. Interestingly, the friendship between Klaus and Bill is stronger than either, and Klaus is determined to protect the naive Bill from the untrustworthy Lucrezia. He fails, bigtime. Bill insits on naming his and Lucrezia's son "Klaus".
Then there's the current generation of Sparks, with Klaus's son as Betty, the son of Lucrezia's most fervent supporter (besides the spider-riding people who worship her as a goddess...) as Veronica, and Bill and Lucrezia's little girl as Archie.
Played with/deconstructed/ripped apart/critically examined (it's the way of their tribe) in this strip of XKCD.
In General Protection Fault, there is initially a love triangle between Ki the Betty and Trudy the Veronica over Nick, who is torn between his feelings for the two of them and his lack of experience in dating and romance.
Dora being mentally healthy and straightforwardnote though she eventually turned out to be more screwed-up than she appeared would be the Betty to Marten's Archie. Distant, emotionally impaired and mysterious Faye would be the Veronica. Dora wins.
Additionally, Angus has emerged as the Betty and Sven as the Veronica to Faye.
And recently, we have Marigold (Betty) and Faye (Veronica) to Angus.
In Penny and Aggie, idealistic Aggie is the Betty, and cynical, venomous Karen the Veronica, to Marshall.
Similarly, quiet, bookish Duane is the Betty, and rough-edged sk8er boi Rich the Veronica, to Penny.
Also, theoretically, the original point of the comic is that Penny is Veronica and Aggie is Betty (or the other way 'round, arguably, as Aggie's goth-ness could make her seem dark and mysterious). Their animosity stems from this difference, though there's no Archie between them.
In El Goonish Shive, Elliot happened to fall for both fellow (and stronger) martial artist Nanase and Sane Girl of the cast, Sarah. The triangle remains only for about five minutes after they all discover what's going on, though.
In the current arc Sarah and Elliot have just broken up and this has brought the attention of Susan and Diane, who are already blatant foils of each other. However, which one is Betty and which one is Veronica is unclear, as...
Susan and Elliot have been friends for a while already. Diane, on the other hand, barely knows him, although she does know Ellen. Also, Susan dresses in average clothing, Diane... well...
On the other hand, Diane is a lot more active in pursuing Elliot than Susan is. Not to mention, Diane is blonde while Susan is dark-haired, like the Trope Namers.
Misfile: Emily (the sensible Betty) and Missi (the wilder Veronica) both like Ash.
In The Dreamer, Bea finds herself trying choose between 21st century Ben and 18th century Alan, with Alan as the Veronica and Ben as the Betty. However, the twist is, that Ben is the "safe" one, but family-loving, apple farmer, puritan Alan probably has more Betty characteristics than Ben, so which is Betty and which is Veronica depends on your interpretation and the situation Bea is in.
It is also worth noting that even in the 18th century segments of the comic there is still a Betty and Veronica dynamic with Alan (Betty) and a young Alexander Hamilton (Veronica). Although, it's pretty obvious which one Bea loves best/chooses.
Gender-flipped in Goblins, with the cowardly Dies-Horribly and the Heroic Gremm both vying for the affections of Saves-A-Fox.
Sandra and Larisa from Sandra and Woo as Betty resp. a particularly chaotic Veronica. In this case, the Archie (Cloud) seems to clearlyprefer the Betty.
In Monsieur Charlatan, the blond Magda descends on Isidore, catches him trying to commit suicide and neglecting to feed his cat, while the dark-haired Adeline is why he was thinking of suicide.
In Faux Pas, the pleasant and reliable Cindy vs. the self-absorbed Dusk. Randy's naivity is probably what's keeping the triangle going.
Girls Next Door features (among others) Christine, Erik, and Raoul from The Phantom of the Opera. Like in their canon, they form a love triangle with Christine as Archie, Raoul as Betty, and Erik as Veronica. The comic explores this trope, and Christine gives a great speech about it:
Christine: Erik is—the rush and the beauty and the joy of it—making music. Erik's part of that feeling for me and part of me and I can't not love him just as I can't not sing. I sang my heart out for him when I believed him my angel—not something that doesn't leave a mark. And I adore him and worry for him and wish him well but Raoul is the warm presence by my side, when I step off-stage, that I can joke and bicker and love and live with—someone who knows me rather than idolizes me.