Different Search Categories - Messages, People, Tags (Tag Cloud)

Currently the search on the top left gives you only the option to search for messages using a free input search field. However, it would be nice if it provided some sub-categories, like searching for messages or people. (The people search would be a handy complement to #[293], in which private discussions could be started with multiple people by choosing names from a list of people).

Additionally a search in the form of a tag cloud would also be useful as a way to see existing tags and how frequently they are used, allowing the user to click on a tag and see corresponding messages, as an alternative to searching by tags.