Up in the second floor of the first building you see when you arrive, a man will give you a Poke Ball. Woohoo. There's also a person in the very back of the second floor who will quiz you on a Pokemon's height and weight. If you guess both correctly (each is a yes/no question), she'll reward you with a Gem of that Pokemon's type.
A man in the upstairs of the adjacent house gives you a BalmMushroom when you talk to him, which is great, because you can sell that for $25,000 by selling it to the maid in the RV on Route 5.
Inside of the house up the stairs, the people there will change the melody of the town's music slightly when you talk to them.
There's a Max Repel hiding in the trash can by the benches in the center of town.
The house down the stairs south of the little park has a Lass in there who will trade an Ambipom for your Excadrill. Its a Jolly nature, holds a Sitrus Berry, and is at level 40, so it's your call if you want it or not.
Well, that's all there is to do in town, surprisingly. Whenever you're done and all healed up (the Pokemon Center is pretty easy to find), head on south onto Route 1.