I've been carrying Yoshimo's heart around for a while now, and I am still unable to figure out what I'm supposed to do with it. Anybody know?

Bring it to a Temple of Ilmater (spelling??), there are two located in the city, one in the Promenade and the other in the Slums. Tell the prist your story and ask him to help release Yoshi's heart.
Hope that helps.

Thanks Accord. Do you get experience points as well?

Yes.....quite a number too. Can't remember what exactly it is....but it's a lot considering just a delivery service you have provided.

90k was it. Or was it 60k?

Alright, thanks, sounds like a good deal! Could always use more experience points!

Actually, when you pass the heart into a temple, you get a whopping 200,000 Experience points! : )