Fluid
With Fluid, you can create SSBs (Site Specific Browser) to run each of your favorite WebApps as a separate Cocoa desktop application.
Stainless
Some features of Stainless:
Parallel sessions allows you to log into a site using different credentials in separate tabs at the same time. This new technology is woven throughout Stainless, from the private cookie storage system, to session-aware bookmarks that remember the session in which they were saved.
Multi-processing architecture in response to Google Chrome.
2 of my favorite browsers on Mac. Just wanted to share that.
Both have the WebKit tech, Web Inspector.

