Excellent Product - Great Support
I've been using the Colligo Contributor Client and their Outlook Add-In for about two years now and am very happy with it. I started off using the Client for offline storage of documents and lists, then moved on to using the Outlook Add-In more intensively.
In my previous company, I used the Add-In to save emails that were relevant to a particular project, and set up Outlook rules to automatically move emails from certain people to the relevant SharePoint libraries.
Now, I tend to use it as a kind of mini CRM system. Each customer has a SharePoint library, where I store both emails (dragged & dropped there with this Add-In) and other documents.
The best thing about the Colligo add-in (apart from the obvious offline functionality) is the metadata support. Colligo delivers attributes like "From", "To" and "Subject" to the SharePoint server, so I can see this information easily if these columns are present. If not, I can simply edit an XML file so that the email subject line lands in the "Betreff" column (that's the German word for "Subject"). I needed to do this at my previous company where no-one else spoke English, but now I stick to the English terms... :-).
Easy to install and connect to SharePoint libraries
Drag&Drop Emails (inc. metadata)
German language interface (I think they have French and a couple of other languages as well)