hobbydog's photo is 800px wide, and it does fit nicely. You'll notice that if you upload an image to this site, it will automatically create the appropriate sized thumbnail that you can click for full view (play around with attachment vs image upload).
Popular photo sites offer multiple embed options, to include 800x600.. requiring zero resizing effort from your computer. figured you would know this already :).
Maybe I'll get ambitious tomorrow and change it to 1000px wide so you see what I'm talking about with the css formatting and page width.