Your requirement that the system needs to work in disconnected environments as well as online, pretty much rules out any web based applications. The application that does what you need and does the best job of dissolving distance and time issues for workgroups is Groove (as was mentioned previously). I've used it in workgroups successfully where we ended up never meeting f2f. That's pretty amazing. It provides synchrounous and asynchronous communication and collaboration tools, synchronizes workspaces well for disconnected uses, has a good alerts system that pushes events to workgroup members, and is flexible and customizable depending on your needs. The alerts really help workgroup members stay connected with each other and with the project. It's not free and it only works on Windows, but it does what you need it to do. If nothing else, download the demo version with a few of your team members and check it out. I think now that Ray Ozzie has joined Microsoft that we'll see a lot of Groove's tools migrated to Office in a less monolithic form than Groove perhaps using web services types of tool integration.