1. Backpack,
2. Tada list,
3. Writeboard
(and no longer offers a free version of Basecamp).
The announcements can be found here:
- http://37signals.com/tadalist-retired
- http://37signals.com/writeboard-retired
- backpackit.com
37signals now ONLY offers products that you must buy.
No more freemium sales model.
As well as they are leaving thousands of Legacy Basecamp customers stranded who don't want to migrate to the new Basecamp product.