Examples of Elgg sites with developed wikis/editable, collaborative, multi author knowledge management

Can folks please point me towards examples of sites using Elgg with extensive, useful "wiki" style articles?

Specifically, content and articles that are multi author, collaborative, editable, taggable, searchable, show revision history, "look good" and are intuitive to use and "user friendly".

Please let me know if I can ssk this in a bettet way, or provide further information.