If you like "Millicent Min, Girl Genius"...
I have not read Millicent Min, Girl Genius yet but it sounds funny. It won the Sid Fleischman Humor award for 2004. The author has written a sequel but it has not been released yet. Be on the lookout for:
Stanford Wong Flunks Big-time by Lisa Yee
Stanford Wong is having a bad summer. If he flunks his summer-school English class, he won't pass sixth grade. If that happens, he won't start on the A-team. If *that* happens, his friends will abandon him and Emily Ebers won't like him anymore. And if THAT happens, his life will be over. Then his parents are fighting, his grandmother Yin-Yin hates her new nursing home, and he's being "tutored" by the world's biggest nerdball Millicent Min.
You may also want to try:
Lily B. on the Brink of Cool by Elizabeth Kimmel
Summer vacation looks like it will be uneventful for 13-year-old Lily Blennerhassett—her best friend went to camp and her parents only believe in educational family outings. For an aspiring author, this doesn't give Lily much interesting material to write in her daily journal. Everything changes when Lily meets a family of distant relatives at her cousin's wedding. The LeBlancs and their teenage daughter Karma are sophisticated, glamorous, exciting, and totally cool.
Alice, I Think by Susan Juby
Fifteen-year-old Alice keeps a diary as she struggles to cope with the embarrassments and trials of family, dating, school, work, small town life, and a serious case of "outcastitis."
How My Private, Personal Journal Became a Bestseller by Julia Devillers
Fourteen-year-old Jamie is tired of feeling insecure: at home she's barraged with media images of physically flawless young women; at school, she's hassled by a gang of catty, manicured classmates. Venting her frustrations in her diary, she chronicles the adventures of invented superhero Isabella (IS) who, with her signature wrist flick, sends "positivity rays" that destroy her nemesis, Myrna, and her "evil clique of Populars." Through a wild chain of events, Jamie's IS stories become a published best-seller, and Jamie becomes a teen celebrity.
You may also enjoy the Princess Diaries series by Meg Cabot if you have not read any of them yet.
You can find more great titles at http://teens.librarypoint.org/reading_matters/