Google Wave

Like Google, Google Wave uses advanced operators for it's search functionality. Wave allows users options to search with advanced operators by Keyword, Status, Participant, Date, Folder, Attachment, Tag, Gadget, Expression, Phrase, XML, Wave ID, Inbox, Saved Searches, Filters and more. Earlier today, a "quick guide to the operators and restricts supported by wave search" was added to Google Wave user accounts.

Here is a screen shot of Google Wave's advanced search operator cheat sheet: