These are great little girl books. The stories aren't quite as girly as some of the other books aimed at younger girls, but they are much better written. The mystery series is kind of fun, because the stories are different from those in the regular series.
I've only added links to the books that I own - I'll get to the rest later.
1 - Stacey and the Missing Ring (Baby-Sitters Club Mystery, 1)- Stacey is accused of stealing a ring while baby-sitting.
2 - Beware, Dawn (November 1991) - Dawn receives threatening notes and phone calls while baby-sitting, all while competing for Sitter of the Month.
3 - Mallory and the Ghost Cat (February 1992) - Mallory finds a potential 'ghost' cat.
4 - Kristy and the Missing Child (May 1992) - Jake Kuhn is report missing, and Kristy was the last person to see him.
5 - Mary Anne and the Secret in the Attic (Baby-Sitters Club Mystery, 5) - Mary Anne uncovers a dark family secret.
6 - The Mystery at Claudia's House (November 1992) - Weird things are happening to the Kishi family when Claudia's room is ransaked and her sister is caught lying to their parents.
7 - Dawn and the Disappearing Dogs (February 1993) - Dawn's pet-sitting charge and Kristy's puppy go missing, and the baby-sitters know it's more than a coincidence.
8 - Jessi and the Jewel Thieves (April 1993) - Jessi visits her friend Quint in New York City and when they overhear two men discussing a jewel heist, they have to investigate.
9 - Kristy and the Haunted Mansion (June 1993)
10 - Stacey and the Mystery Money (August 1993) - There's conterfeit going on in Stoneybrook and, when Stacey ends up accidentally paying someone fake money, the BSC have to clear her name.
11 - Claudia and the Mystery at the Museum (November 1993) - Claudia is visiting Stoneybrook's new museum when several thefts occur. Claudia has to find the culprit and save the museum!
12 - Dawn and the Surfer Ghost (Baby-Sitters Club Mystery)- Strange things are happening when Dawn sees a ghost off the California coast.
13 - Mary Anne and the Library Mystery (February 1994)- Mary Anne gets a job helping with the children's read-a-thon at Stoneybrook Library, where someone is setting books on fire! But who?
14 - Stacey and the Mystery at the Mall (April 1994) - The baby-sitters are working at the Washington Mall for a class, and they begin to wonder if it's safe to shop there after a string of expensive thefts happen.
15 - Kristy and the Vampires (June 1994) - Accidents, mysterious letters, and rivalries on the set of a TV movie being shot in Stoneybrook add up to trouble for Kristy.
16 - Claudia and the Clue in the Photograph (August 1994) - Claudia unknowingly takes pictures of a bank robbery in progress that end up being the only clues to catch the crooks.
17 - Dawn and the Halloween Mystery (October 1994) - Trick-or-treating is being called off after a robbery in Dawn's neighborhood, unless the We Love Kids Club can catch the robber.
18 - Stacey and the Mystery at the Empty House (December 1994) - Stacey is house-sitting while the Johanssens are away, only to begin suspecting she is not alone.
19 - Kristy and the Missing Fortune (February 1995) - Kristy digs into Stoneybrook's past and discovers the story of a young heiress who disappeared and took her fortune with her.
20 - Mary Anne and the Zoo Mystery (April 1995) - A school trip takes Mary Anne to the zoo and a mystery arises when they discover someone has been letting animals out of their cages.
21 - Claudia and the Recipe for Danger (Baby-Sitters Club Mystery) - Someone is sabotaging the baking contest
22 - Stacey and the Haunted Masquerade (October 1995)
23 - Abby and the Secret Society (February 1996)
24 - Mary Anne and the Silent Witness (April 1996)
25 - Kristy and the Middle School Vandal (June 1996)
26 - Dawn Schafer, Undercover Baby-sitter
27 - Claudia and the Lighthouse Ghost (December 1996) - Old friends of the Kishi family come to stay with them, which unveils a terrible story of something incredibly creepy that happened a long time ago at the old Stoneybrook lighthouse...
28 - Abby and the Mystery Baby (February 1997) - Abby's family takes in a baby left on their porch while authorities look for the parents.
29 - Stacey and the Fashion Victim (April 1997) - Accidents and threatening notes plague Bellair's Fashion Week and Stacey has to figure out who is behind the events.
30 - Kristy and the Mystery Train (June 1997) - Three baby-sitters embark on a mystery tour with Derek Masters, but someone is determined to ruin their good time.
31 - Mary Anne and the Music Box Secret (August 1997) - Mary Anne finds a package hidden in the basement of her grandparents' house. Ignoring the curse written on the packaging, she opens it to discover a beautiful music box: just before odd things begin happening.
32 - Claudia and the Mystery in the Painting (October 1997) - Claudia must search for paintings that everyone swears the artist destroyed before her death.
33 - Stacey and the Stolen Hearts (February 1998) - Someone steals a bag of valentine-grams and begins revealing the very personal content on them.
34 - Mary Anne and the Haunted Bookstore (April 1998) - Mary Anne gets a job at a bookstore, only to discover happenings that aren't just fiction.
35 - Abby and the Notorious Neighbor (June 1998) - Abby becomes convinced that her neighbor is a thief, and tries to gather evidence to take to the police.
36 - Kristy and the Cat Burglar (August 1998) - When a cat burglar strikes a Stoneybrook mansion, Kristy and her friends must work to solve the crime before the thief gets away.