When you acquire the shovel while looking for the flute, there is an oprotunity to use it for some good gains. Head to the Dark World, and there you will find a guy who will allow you to dig for treasure. You will have 30 seconds to uncover as much as you can. And whatever you unearth is yours to keep. Be warned though, that once you lose the shovel, (When you get the flute) you lose the ability to dig.
Reward: , 's, 's, 's,

In Kakariko Village, there is a home with 3 chests in it. At the cost of 20 Rupees, you can open one of the 3 chests. The amount is set, and you can only get 1, 20, or 50 rupees back.
If you have the extra dough, this is kind of a fun little gambling thing to do. If not, this is certainly not the greatest way to make money, as the odds of winning 50 rupees are 1/3.
Reward: x1 x20 x50

Ok, so there is a little bit of a race going on. You need to get through the little maze to the end in 15 seconds. It is pretty easy...but in some ways it is not. You have to go pulling grass for starters. There is no way around it, and very little way of being able to dash through a lot of it. Not to mention bouncing off something will shave 2 seconds each time you do it. Just go through the grass, memorizing the correct path. Once you do, there should be no issue getting to the end of the maze.
Reward:

In the Village of Outcasts, there is a shooting range, where you ccan test your archery skills for 20 rupees. It is your skill alone that will determine what you get. If you are a great archer, this can be a good money maker, as the profit is up to 44 rupees for each turn. If you are not a great shot, it could be fun if you have the extra money, as well as being somewhat helpful in learning how to aim on a mmoving target.
Reward: 4 's, plus 2 's for each target hit. (Total of 64 's)

In the Village of Outcasts, there is a chest game as well. The cost is also 30 rupees to open two. This one though is more sensible to play. Not only is there a chance of recieving a Heart Piecec, but there is other prizes. The heart Piece does make this a must do mini-game though.
Reward: , 's, 's, 's,