We use Pivotal, Skype, Whatsapp, Github, Zoho (CRM/Projects), Dropbox. Of all these Pivotal + Github seem to be by far the highest on the list; without those we would be dead.

We have some glue tying these together and we use some in-house development wiki's and live-editing tools for producing faster and collaborating better.

Thanks for wemux; that looks really great :)