PC - Purchased through 2D Boy's site

Download and run the patch: http://goofans.com/download/utility/world-of-goo-update

PC - Steam

Steam will automatically update it to 1.20. If you want 1.30, download the patch from here: http://goofans.com/download/utility/world-of-goo-update

PC - Retail box

Download and run the patch: http://goofans.com/download/utility/world-of-goo-update

Wii

There is no patch for Wii. However almost all the changes from 1.00 to 1.30 are for PC anyway, so there is no need for one. The only significant change is that you can now replay MOM's Computer, but 2D Boy are unlikely to release a patch just for this.