'Scholarly' alternatives to Goodreads

There indeed is plenty of web sites where you can shelf articles, preprints, etc. (Mendeley, Zotero, CiteULike, and so on; a fairly comprehensive list is available on Wikipedia) but if you also would like to have the possibility of adding reviews like in GoodReads, the things are somewhat different.

One site that I know of that allows you to do this, in addition to merely bookmarking the items, is ResearchGate with its Open Review feature, but you can only bookmark and review items that already are in their database (you can add the articles that you (co-)authored but I doubt that reviewing them is your intention). Perhaps there are some other sites with a similar functionality: e.g. according to Wikipedia CiteULike has it too; on Mendeley you can share articles' annotations within private groups.

Also, there is a number of sites allowing you to bookmark and review arXiv preprints (e.g. SciRate) but not the other kinds of items like the books.