As a system administrator, I do a lot of research on websites during my workday. I often have many tabs and windows open at the same time. I am also sometimes constantly interrupted by people who need help, or sometimes I need a reboot. I have wanted to see a feature called 'Save this Safari session' for a long time -- so that I could quit Safari and return at a later time to finish what I was doing. (Finding relevant websites/articles is part of the work I do. When I have to quit Safari, in a sense, it's like a copy editor starting a new chapter over again.)
Although Safari 3 didn't come through for me completely, they did add one feature that gets me part of the way there, and I have found more than one use for it. The History » Reopen All Windows From Last Session command is that new feature, and it's all we have for now. Beyond the expected uses (Safari unexpectedly quits with many windows/tabs open; or I have to reboot my system), here's a way to use it in conjunction...