The first demo at the TechCrunch 40 conference today is from Xobni ("inbox" backwards, oh how clever), which makes the "Insight" plug-in for Outlook that looks like it will be worth installing when it opens up to the public later this fall. When you highlight an e-mail, it gives you useful intelligence related to the sender: other messages from him or her, who the sender is connected to (via cc), and a graphic showing when the sender's previous e-mails have been received.
It also extracts phone numbers and other contact info from e-mail message bodies and lets you search your e-mail files and attachments.
The part of the pitch that really hooked me: "Xobni exposes the hidden social network" in your e-mail. I totally get that. Our in-boxes really do contain a lot of social information, and I am very eager to see if Xobni will help me uncover mine.
I installed a preview version of this app and am looking forward to stress-testing it in the next few days.