http://www.getsoloapp.com/

https://www.atlassian.com/software/jira/

https://asana.com/

http://kickoffapp.com/

https://trello.com/

https://www.flowdock.com/

http://www.getflow.com/

https://www.activecollab.com/index.html

http://lighthouseapp.com/

https://www.producteev.com/

http://fuelcollective.com/eon

https://duetapp.com/home

http://updatey.com/

http://www.dobambam.com/

https://ding.io/

http://www.usepeak.com/

http://www.invisionapp.com/

http://viewflux.com/

http://www.getblimp.com/

https://podio.com/

http://www.conjure.io/

This question has already been asked (app for managing projects in a group of less than 20 people), you can find interesting answers here:

• "Ask DN:" Project Management Systems
• Ask DN: What's the best tool for managing projects?

I hope it will help you!

I've used, and enjoyed, Asana.

We're about to launch something new: Forecast

It's a project management app that marries Trello-like, easy to understand interface with the structure of a more traditional project management workflow (i.e Basecamp) Designed mostly for ourselves and friends at various startups and agencies: something light and flexible that doesn't have unnecessary bells and whistles. So it's decidedly not suitable for large companies.

Sign up for a free account if you guys want to test drive. We'll be rolling out private beta invites in coming weeks!

I've been using blossom.io which has been pretty great so far. Blossom+Slack is a killer combo.

Trello/Slack/Dropbox/Glip/Peak

We're using Basecamp, very basic but almost no familiarization time for third parties.

https://basecamp.com/