Here is the full list of all 8 World of Goo achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
All OCD Flags in Chapter 3
All OCD Flags
All OCD Flags in Chapter 2
All OCD Flags in Chapter 1
All Levels Complete
All OCD Flags in Chapter 5
All OCD Flags in Chapter 4
there is a secret