Hoshi no Koe Haruka na Machi e - Doesn't have much romance. Just a crush. Highly recommend this story though the girl and her ambition are not the main point. Bakuman - Girl wants to become a voice actress.
Uwasa no Midori-kun!! - I don't like it, too smutty, but the girl wants to beat her childhood friend in soccer (he tricked her into having sex for a bet when they met years later) Honey Hunt - girl wants to be an actress to beat her mom (I don't think anyone is scanlating right now) Beauty Pop - girl wants to be a beautician/hairstylist. Cute. Sugar Princess - girl wants to ice skate (on hiatus) by same author as Hana Kimi (Hana Kimi is AWESOME) Kitchen Princess - girl wants to cook The One - model Charming Junkie - model Venus Capriccio - ambition doesn't show up until later, mostly it's the guy who ends up wanting to succeed - piano. Very sweet manga. Kiniro no Corda aka La Corda D'oro. Didn't like it much, but a lot of people love it - wants to become violinist (doesn't realize she actually wants to until a little while in though)