I have been using the Outlook search add-on by Xobni for the past few months and I have to say it is a great time-saver for me. It is lightning quick in searching my Outlook email compared to the built-in search Outlook provides.
In addition to the search capabilities, Xobni allows you to better navigate your email world. When you are viewing an email in Outlook, Xobni will display the contacts phone number (and a link to call if you have skype installed), recent conversations and recent attachments.
Have a look at the following youtube video to see all the features of Xobni.