[conanite]

Add this to your browser's search engine list and make it default:

    {google:baseURL}search?q=%s+-site:pinterest.*

[wyclif]

If on Firefox, do you need to add the optional search bar (with the magnifying glass) in order to access "Change Search Settings"? Because I'm not finding it anywhere.

[LordDragonfang]

Doesn't help with reverse image searches, which accounts for probably 90% of the times I end up clicking on a pinterest link.

[richardfey]

That's a brilliant solution, thanks!