Trailhead is an awesome resource for many reasons! It is awesome for reviewing questions on common use cases and functionality.
The Lightning Club has resources beyond the scope of trailhead. From courses to improve your freelance revenue, to live-forum answers answering detailed use cases with CURRENT information, aggregated freelance job postings from multiple platforms, and much more, this is a powerhouse addition to the knowledge bases available not only to Salesforce professionals, but especially freelancers.