I really, really like One Piece too...the manga is quite exceptional. *nods*
Hmm...as for manga, the only other thing I can think of that involves following a dream is Kitchen Princess, but it's a shoujo (I think) drama, and I'm not sure that's something you'd be interested in. (I'll be working on a review for it, btw, as the last--I believe--book comes out next month)
Now, if you don't mind me recommending an anime, Comic Party (the original, dubbed by RightStuf) is pretty good. Like the guy who reviewed it said, it actually inspires the viewer to do or make something; he was inspired, and I felt like I wanted to sit down and either write or draw manga as well. Granted, I'm recommending the anime because I heard the manga had fanservice in it, and while the anime may not be completely devoid of it, the manga had more I think. And I haven't actually read the manga. But as I was saying, I'm only recommending this because it's one of (if not the only series) that actually stirred up inspiration inside me to get up and do something (and since I like to write that's what I wanted to do). So yeah, sorry I'm not recommending the manga, but I'm not sure about it (because of the fanservice).
RESPECT THE UNBORN AND CHOOSE LIFE...your mother did.
"Do not underestimate the power of the muffin! The muffin will smite all those who question it! The muffin will crush all nay-sayers! He who controls the muffin shall control the entire world!" -Taishi, Comic Party English Dub