Crop finder
A Gold Club map search over tiles the server has already classified as high-crop.
Stock Travian
Finding a 15-cropper is a manual map crawl, or a third-party tool.
Travikas
Gold Club search over tiles already marked as high-crop. It does not mean the tile is empty or that you can hold it.
When to use it
Before you train the second set of settlers. On a 25×25 the good tiles are known on day one. If a cropper is already taken, you are looking at a conquest, not a settle — read conquest first.