i am addicted on konqueror 3.2
When you middle click on one link, or when a javascript tried to open a new window, you can default open a new tab instead a new window. When you try to click on the cross and have many tabs opened, it asks you "do you want to close the tab or the window". It also contains a nice password management utility, which is protected by password (like a passport), and much more.

I think it is available for most unixes, especially Linux. go to konqueror.org if you are not using windows...

:-)