One great thing about Firefox (and presumably IE7, though I admit I don't know) is the ability to open a group of bookmarked, tabbed websites at the same time. This saves all sorts of time when you have related websites that you want to view all in a set.
One downside to Firefox (and presumably IE7,
though I admit I don't know) is that you are forced to open the entire group of bookmarked, tabbed websites at the same time. This creates all sorts of headaches when your related websites are image-intensive or assembled on slower servers.
I propose an intermediary step: a new tab is created, with the desired URL in the address bar, but not yet contacted or loaded. Clicking the "go" button, when you want to view this particular site, allows you to load it, but not until you're really ready.
This function would be accessed through the bookmarks dropdown, and would be directly underneath or directly above the "open all in tabs" command.