[se6]

For Exchange-based email you can use DavMail (http://davmail.sourceforge.net/) At work I have the only Linux workstation and DavMail + Thunderbird + Lightning works a treat. I have pretty much all the functionality that my Outlook fellows have. (email, calendars, LDAP corporate address book, etc...)

[toxican]

Ah! That is seriously cool and it only took like 5 minutes to get up and running. I don't suppose there's a way to support Tasks?