Camino, the open source Mac browser based on the Gecko layout engine that bills itself as having Mozilla Power, Mac Style is out in a new version 1.6. The browser features feed detection, integrated search, saved sessions, and spell checks.
Well-liked for its snappy performance, Camino doesn't have the market share that Firefox does, but many Mac-based open sourcers use it. Check out Om Malik's summary on GigaOm.com.