One really great browser concept that I can’t stop thinking about: http://live.gnome.org/Epiphany/FeatureDesign/DesignConcept
Basically, it aims to keep the user focused. It replaces tabs with “queued pages”, which are directly related to the current page. You navigate through queued pages and your history spatially.
As a person who frequently gets lost in his tabs, and as someone who can get distracted online really easily, I would really, really love if this interface came to fruition.