There are a number of services, free and paid, that attempt to improve aspects of your email software.
Xobni is my preferred program for Outlook. I have found the search capability incredibly useful. At present I am a beta tester for Xobni for Gmail and again I am impressed by the integration into gmail and the search functionality. It is interesting when you consider that Google is the No. 1 Search provider on the planet yet the reality is others can take Gmail and improve the search function. Makes me think about execution.....
Other tools use may want to consider:
Email Social Connectors - Gist, Rapportive
Tasks = Remember The Milk, Toodledo
Contact Manager - There are a bunch out there but considering what they charge I'm happy using Outlook Contacts
Finally if you are in to GTD (Getting Things Done) have a look at Jello Dashboard. Considering it is free it is very impressive.