In the comments, please share some of yours.
Prada and Prejudice by Mandy Hubbard.
To impress the popular girls on a high school trip to London, klutzy Callie buys real Prada heels. But trying them on, she trips...conks her head...and wakes up in the year 1815!
There Callie meets Emily, who takes her in, mistaking her for a long-lost friend. As she spends time with Emily's family, Callie warms to them - particularly to Emily's cousin Alex, a hottie and a duke, if a tad arrogant.
But can Callie save Emily from a dire engagement, and win Alex's heart, before her time in the past is up?
Death Comes to Pemberley by P.D. James.

But on the eve of the ball, chaos descends. Lydia Wickham, Elizabeth’s disgraced sister who, with her husband, has been barred from the estate, arrives in a hysterical state—shrieking that Wickham has been murdered. Plunged into frightening mystery and a lurid murder trial, the lives of Pemberley’s owners and servants alike may never be the same.
Pride, Prejudice and Jasmin Field by Melissa Nathan.

And nobody is more surprised than Jasmin herself when she lands the role of Elizabeth Bennet. But things start to go very wrong very quickly. Ms. Field's delicious contempt for the arrogant, overbearing Harry Noble goes from being wicked fun to infuriating.
Her brief moment of theatrical glory looks as if it's going to be overshadowed by the betrayal of her best friend, the disintegration of her family and the implosion of her career. And suddenly she can't remember a single one of her lines. But, worst of all, Harry Noble -- who, incidentally, looks amazing in tight breeches -- has started to stare hard at Jazz with that sort of a glimmer in his eyes...

What would happen if Jane Austen's Pride and Prejudice was set in the twenty-first century?
When Mrs Bennet inherits enough money to move to the kind of village she has always dreamed of, her daughters find themselves swept up in a glamourous life of partying and countryside pursuits.
But Lizzie and her sisters soon discover that, beneath the very smart surface, lurks a web of intrigue and rivalries . . .