In Firefox you can add an icon to the toolbar which when you click on it opens a new tab. I too liked IE7's feature but am happy with Firefox when I found this. Go to view - toolbars - and drag the icon to the toolbar.
I'm an IE7 fan too, have tried Firefox, but we just didn't click. I usually have at least two tabs open and a blank 'ready to go', right now I'm waiting for a cenus image to load in Ancetry.co.uk, which gives me the opportunity to come here and annoy everyone, and then I will have three or four tabs open to cross reference the census image.