I first read about Lookout in Omar's post, Outlook is a platform.  I use it everyday to search my Outlook 2003 inbox, calendar and contacts.  Microsoft just announced today they bought Lookout: http://biz.yahoo.com/rc/040716/tech_microsoft_search_1.html

“Lookout is a small software add-on to Microsoft's Outlook e-mail, contacts and scheduling program that allows users to bypass the search tools provided by Microsoft and sift through e-mail, contacts and other information with keywords.”