Aside from the Shines collected in the game's many episodes, there are others dotted around Delfino Plaza, mostly as rewards for completing mini-quests or secret levels.
If you go inside the boathouse that the portal to Ricco Harbor is painted on, you'll find talking bear and his/her son/daughter. The bear will give you Shines in exchange for 10 blue coins, which you can find all over the game. So every time you collect enough blue coins, come here for some bonus Shines. Check the Blue Coins section of this guide for information on where to find them.
Near the tower on the beach in the north-eastern part of Delfino Plaza, you will see a group of stone pillars sticking out of the ocean, just a little way offshore. Jump and hover to reach the pillar that has a big green pipe sticking out the top. Climb into the pipe the start a relatively easy secret level. At the end of the level there's a Shine waiting for you.
Climb up on to the roofs of the buildings and explore until you find a Pianta man standing on one them. He is on the beige-coloured building on the corner of the river/harbour area. The picture to the right shows Mario looking at this building. Once you get to the roof of that building, the Pianta will asking for one coin in exchange for throwing you into the tower opposite. Once in the tower you'll find a shiny new Shine.
If you've been looking closely you'll have noticed a couple of bell towers dotted around Delfino Plaza and that the bells housed in these towers are covered in black goo. The screenshot on the left shows the tower with the bell that Mario must clean to get this Shine. It's not difficult to find as it is pretty much the tallest tower around. If you stand in Bianco Square, facing the portal, then go left past the line of trees, you'll come to a white building with a huge wooden tower on the roof. This is the tower but getting to the top is more tricky.
First you need to climb the tower directly opposite (a few well timed back-flip jumps and use of the hover nozzle should get you there) until you reach the very top where the flag is. Now hover-nozzle over to the bell tower and clean off all the goop. When it's fully cleaned a Shine will appear in the tower below the bell. To get to it you have to go through the manhole cover which is on the roof of the nearby building (the next to the huge wooden crate).
The picture on the right shows where the manhole cover is in relation to the tower. Once you find it, stomp through the manhole cover and follow the tunnel to collect your Shine.
To the left of the huge Shine Gate in the tower centre, there are a few shops. One of these has a black entrance where its door should be. Walk through it and speak to the Pianta inside to play the crate-stomping game. You get 30 seconds to smash all the crates. It's free to play and you get unlimited attempts. Tip: stomp the join between 2 crates that are next to each other and you can smash them both in one go.
You can go straight back into to the crate-stomping game to play a harder version and win another Shine. This time the boxes are stacked up: 2 stacks of 3 and 2 stacks of 2. It's best to go for the stacks of 3 first - using a back-flip jump to get the top of the stack. Then take out the remaining 2 stacks. It takes some practice to do it within the time but it's not too difficult.
On the beach next to the portal to Gelato Beach (the lighthouse), there is a patch of sand which you can spray to reveal a Shine. The picture on the right shows where this patch is. When you've uncovered the Shine it will appear on a pillar just offshore.
You may have noticed that underneath the bell tower (the one you sprayed the sludge off earlier) there is a Shine in a small room protected by small double doors. If you have unlocked the Turbo Nozzle by now, you'll be able to get this Shine. Stand back from the doors a bit and charge up the Turbo Nozzle. When it releases, you will blast through the doors and Shine is there for the taking.
Just off the east beach (the one where the man offers you sunglasses) there is a small island with a Pianta and a green pipe on it. Swim out to the island and you should see a little yellow bird, either sitting on the sand or flying around above the tree. Spray the bird a few times and a Shine will appear and one of the stone pillars further up the coast. Use hovering to reach the Shine.
Also, on this island, you can spray the small log fire to release a 1-Up mushroom.
When you get the fruit boats unlocked, use yoshi to ride to the island with the yellow bird and the campfire. This is fairly hard, you have to jump and travel across 3 boats. Once you get to the first island with the girl Pianta, you can ground-pound and go into the tunnel and pop up on a roof with a fruit. (You know, since you can use up juice while just standing there!). When at the second island (final destination), spray the yellow goop blocking the pipe to find a relatively hard secret level. Once you get the red coins, go to the end of the course and collect the Shine.
Go to the nozzle boxes in Bianco Square and attach the Rocket Nozzle. Then look to you right to see the jail house, with a smallish ball tower on top of it. Run over and use the Rocket Nozzle to boost up to the dirty bell, then give it a good spraying until a shine appears.
Cheekily, the Shine appears high above the bell tower, so you need to climb down a level on to the ledge. From there, boot up onto the roof of the tower and then boost again, straight up, to grab the Shine.
As you've probably noticed by now, the giant Shine in the top of the Shine Gate is covered in filth so it's time to clean it up. Climb the grassy hills behind the Shine Gate until you get to the top level (where the water comes out of a cave). From the round platform here should just about be able to reach the giant Shine with your spray. Clean off all the goo and a Shine appears high above the Shine Gate. To reach it, rocket up to the top of the Shine Gate and stand right in the centre (on the hump part) and rocket straight up to grab the Shine.
Go to the tower on the east beach, where the portal to Gelato Beach is and rocket to the top of the tower. Climb right to the very top and you'll see a black disc on the roof of tower with a flame logo on it (it actually looks like a giant hockey puck!). Stand on the disc, rocket upwards and at the peak of your jump, ground pound the disc to smash it. A Shine will appear above the tower so just rocket straight up and get it.
In the north-east part of town the is a double door with a Pianta guard standing either side of it. It's at the end of the path the runs along the east beach. Use the Turbo Nozzle to blast through these doors and be transported to a secret level. This level isn't too difficult - it's basically just a test of you good you are at using the Turbo Nozzle. Just use the turbo boost all the way and make sure you keep running straight, jumping the gaps when you get to them and make the final leap to the Shine platform.
As you probably know by now, you can earn a bonus Shine in each of the game's areas by collecting 100 coins. Well, you can also do that around Delfino Plaza itself. There are stacks of coins lying about and it's possible to get 200+ coins if you look hard enough (if you go to the airstrip after you've beaten the game to collect the 100 coins there, the total number of coins for Delfino Plaza will increase). The majority of the coins are hidden in Delfino Plaza's network of underground tunnels - there are 98 down there to be exact (plus two 1-Up mushrooms and 3 blue coins). The map on the right shows these tunnels and where the coins are hidden. Other coins are hidden in various boxes, posters and open windows. Here are the locations of a load more coins so you can make it past the 100 mark:
When you've collected 100 coins the Shine appears on a platform out at sea, south of Bianco Square. Swim over to it and use the Rocket Nozzle to boost yourself out of the water and up to the platform, or you can ride one of the boats and do a spin jump onto the platform.