Riffs is a social software site that lets you vote and comment on products, celebrities, websites, places, events and just about everything else. It's like a simplified version of Epinions. The interface is great and it's all very accessible - you'll instantly understand what it's about. Sure, it's an obvious idea, but on this occasion it's particularly well executed. From the site:
Riffs is a place to rate, recommend and review all the things you like and don't like, and to find others who share your interests. You can riff alone or with your friends, family, colleagues and the Riffs community.
Express your opinions on anything by writing a short riff, or a long review, or just look for things that other riffrs have contributed, and rate and/or comment on what they've written. You can also get personalized music recommendations just by rating a few albums!
Riff on... Music, Books, Movies, Cars, People, Places, Events, TV, Sports, Restaurants, Games, Software, Websites... and anything else.
Like Digg, it looks like they want you to use "riff" as a verb. In fact, the two names are remarkably similar if you ignore the pluralization - no doubt the creators were inspired by Digg's phenomenal success.