You can now post new messages to a Basecamp project directly from your email. Users have asked for this for some time, and it will be a most useful feature. Previously, you could respond to a message from email, and now you can initiate a new discussion.

The trick is to find out your unique email address for projects you want to post to and put that in your address book. Here is the explanation from 37Signals:

http://productblog.37signals.com/products/2010/02/new-in-basecamp-post-a...

Love (or like) Basecamp, and just wish you had a familiar toolbar for everyday formatting, such as bold, italics, making lists, and inserting web links? You can download a free add-on to Firefox that will insert a formatting toolbar for use in messages and other common Basecamp pages. You can find it on the Firefox add-ons page or you can get it directly: http://www.toddle.com/basecode2/

Once you have it, and restart Firefox, the formatting options will show up both as a tool bar and as a right-click dialog option.

It works on Windows, Mac and Linux.

Did you know you can export your entire Basecamp project space into an XML file? This is a great personal reassurance feature of BaseCamp. You can at any time pull everything you have put into Basecamp back out into a transportable format. (Well, not everything—not uploaded documents—but definitely everything else.) Go to “Account” and scroll down to “Need to export your data.”

What can you do with all this stuff once you have exported it?  

Basecamp makes it very easy to add "companies" (other organizations) to a project, in additoini to your own company or organization.  And you can add as many users to each company for that project. And once you do that, you can then decide what level of access each of these additional company users should have. You can allow them to see and post messages, to-do's, and/or milestone events.