I just so happen to have a handy list:
Ways to make tu:

Luck games including The Twunty Cay, Random Tu, Rock Paper


Scissors, Mystery Box, and Precious Pearl Quandry.

Skill games including Stocks (buy low, sell high) and Egg Count

Flash Games

Sell pets in your rancher shop (if you are a rancher) or sell


items in your merchant shop (if you are a merchant).

Sell hatches that you don't want to use (they go for 100,000tu


each)

Sell unwanted eggs in the Egg Market.

Sell art if you are good at it.

Go to the  User Contests forum and join different contests.

Use the Sales & Trades forum to advertise what you are


selling.
 Welcome to Res ^-^