Technically it's
http://portal.opera.com, but by default start up to Opera Speed Dial, so I never actually see my homepage. Could set it to Google but from Speed Dial I can just type "g whatever" to Google whatever, and Ctrl+1 (or 2, 3, 4) brings up all my most visited sites, so there's no point in setting one of them to the home page, especially since which one I want to visit first varies.
I could have Opera load to whatever I had up the last time, but I tend to get bunches of tabs up that I probably won't want the next time. Which would eventually require closing them. So it's easier to start from the beginning again.
Just set my secondary browser (in terms of most-used), IE, to Google over the default msn.com, and I've left my tertiary browser, Firefox, at the default home page. IE > Firefox because of compatibility, btw - if Opera doesn't run it, IE will. Firefox falls by the wayside, only use it for Photobucket and once in a long while Googlepages.