Today I tried Mozilla Prism (cross platform) and Fluid (mac only), both of which are used to create single-site browsers (SSBs). I especially wanted to use them for GMail and Google Calendar since those are the two web apps I consistently have open in a tab at all times.
I’m still playing with them both but the first thing I realized was that they would have to do better than use the 16×16 favicons. I was able to extract the official high resolution Google icons from the Google Gears desktop shortcuts for GMail and GCal, so they are attached. These will work for Fluid. For Prism, you’ll have to use the PNGs attached.
Later I found Chris Ivarson’s page with some great icons, but my first couple Google searches didn’t lead me there, and he doesn’t have the standard icons that come from Google.
Edit 1: By the way, I have chosen Fluid because its icon shows me my number of unread messages so I can keep it hidden when I don’t have new mail… very helpful.
Edit 2: By popular request, I just added a Fluid icon for Google Wave also