I would like to see (better) solutions not only for source code, but general web-pages and applications. For example, bookmarks in a browser are ok, but it would be a lot better if you could easily annotate and later reference / rank / prioritize. A browser is a pretty good proxy to the world's knowledge including source code. It be nice if they would level up in these regards.

There are tools for aspects of all these areas, but still feel unsolved (easy, feature-full).