again, I am fascinated by lists of bests, especially as related to literature; they comprise both an ideology of the canon and a sociology of popular tastes, a la Bourdieu; in an extended form, they comprise much of amazon.com
"ShopWiki actively crawls more than 180,000 online stores to ensure you’ll find the products you want at the best prices." For a class looking at web2.0 apps, it's the kind of thing students would enjoy playing with.
social bookmarking portal lets users share expertise on some subject; room for author's comments and explanations; more discursive than delicious; less writing than a blog; see "Visual Thinking," also "Ephemeral Films"