Wunderlist Simple Pretty To Do List
This is a great simple to do list tool. It is web based and you can use a mobile version. If you go with the pro version you can exchange files ($50/year). You can invite people to assign tasks to you, and the tool I like is you can have it send push notifications on your phone (cool).
Create Your Social Intranet For Free With Bitrix24
Bitrix24.com is like having yoru own Facebook for your company. It's also like having dropbox, skype, a CRM, instant messaging, project management, calendars, planners, meetings, etc and if you have less than 12 employees you can use it for free and currently there are over 85,000 people using it.