Exchange 2007 Search
I'm a frequent Outlook Web Access user, even when I'm at work but especially from home or when on a trip. One of the things that I think is best about OWA in Exchange 2007 is it's prominent "search" bar. This makes it very easy to find whatever email I'm looking for -- and since I have 10,000 messages in my Inbox folder alone (since Februrary) -- this is no easy task.
We've posted a Wiki Entry on exchangeninjas.com that describes how server-side search works in Exchange 2007 -- check it out.