According to my study on http://basecamphq.com/ there are many entrepreneurs, business man and clients they admire Basecamp so much. They said that Basecamp is amazing system for project management development particularly Basecamp is easy to communicate each other between owner and clients.
Basecamp's features are:
1. Project tracking with milestone calendar
5. and other forum
Otherwise Google tools is also awesome for communicating, messaging, google docs, chatting, sharing, Groups, calendar, forum and many tools.