Imagine designing a customized search tool that limits hits to sites you know are useful for kids. You can do this now by creating your own Google Custom Search Engine.
This picture shows the widget of a custom search engine on the topic of postage stamps. A teacher can place such a widget in a blog, wiki or shared "start" page for students to use for topical searches. Another remarkably google-y thing? The creator of a custom search engine can invite up to 100 "volunteers" to contribute to and refine it. Imagine having kids develop an operational definition for project-suitable sites to be queried by the engine. That would require critical thinking of a high order!