Wikipedia’s a great resource for learning more about complex or esoteric subjects, but sometimes the dense, insider language can be a bit off-putting. Free mashup tool Again, But Slower compares original Wikipedia entries with their simplified re-writes.
Those rewrites come courtesy of Simple English Wikipedia, a site with over 59,000 Wikipedia articles written for those at early stages of English learning or otherwise needing scaled-down encyclopedic articles. Again, But Slower simply shows those entries and the original Wikipedia entries side by side, allowing you to learn how complex scientific terms and other phrases are being used, and getting a possibly faster-moving read on a subject you need to catch up on.
Again, But Slower is a free service, no sign-up required.