The search function on World History Commons searches the entire site instead of just the primary source collection. The primary source collection itself does have some filters that you can apply as you browse through the collection. You can filter according to region of the world, time period, subject, and source type (audio, image, text, video, or object). The world, time period, and source type filters do exactly what you'd expect. The subject filter is a little trickier because some events could be classified into multiple subjects but might only appear under one of the filters.
The teaching guides section of the World History Commons offers some lesson plans and advice on strategies for teaching with primary sources. The guides are aligned to specific primary sources within the World History Commons collection of primary sources. Your search for teaching guides can be refined according to time period, region, and subject.
Applications for Education
The World History Commons is a resource that everyone who teaches world history lessons should have bookmarked. While the primary sources on their own are useful, the annotations can help students understand the significance of what they're seeing and reading. The teaching guides are also helpful in providing some inspiration for how to use primary sources in a variety of settings. I particularly enjoyed reading through this guide to teaching about Chinese propaganda posters.