My workmate (male) who never read shoujo before quite enjoyed
Nana, from
Ai Yazawa.
Though, the story is unfinished (21 completed volumes), and the author may not write manga anymore due to an illness/accident. she may continue, we really don't have any information from almost 2 years now
She made a lot of other shoujou, you may like :
Kagen no Tsuki : (or Last Quarter) 3 volumes. Children helping a lone ghost who lost her memory searching her identity.
Paradise Kiss : 5 volumes. This manga was pre-published in a fashion magazine instead of a manga magazine. the story cover fashion student's life looking for a model to present their collection.
From
Saki Hiwatari, I like all her work.
You may be interested in
Please save my earth (also known as Reincarnation), though there are a lot of volumes (21+1), and a sequel "Embraced by the moonlight: Reincarnation II" (currently 8 volumes).
The story cover people developing ESP (psychic power) allowing them to remember their past lives, when they lived on the moon. The manga (like ALL the manga of that author) is a dual story, showing present day in one chapter, and past days from their previous lives in the next one, etc.
Her manga are alway dual (present/past, real/dream, etc.)
Chobit, or
Wish from
Clamp.
edit : oh, you certainly already read Chobit if you read everything from Clamp. maybe not Wish, it's a little less known.
Marmelade boy from
Wataru Yoshizumi.
Then, another author I like a lot is
Mitsuru Adachi. He is writing almost only sport's manga, and mainly baseball one, but can be considered shoujo at some point.
He wrote many side story or oneshot too, like
Slow step or
short program, or
Jinbe.
His particularity is that he is always using the same style/same character design for all his manga. It may be strange but I don't mind that.
he is the author of Touch, H2, Cross Game (you should look this anime if you want to know the author's work and style).
a Manga I liked which is not about baseball is "Niji Iro Tougarashi", it's a comedy based on edo era.