At GoAugust we are using a variety of tools to organize ourselves. Among them are FengOffice, Google Docs, Google Talk, and Catch. For real time collaboration on documents and spreadsheets, we use Google Docs. We find it very easy to use and it feels like we instantly have a first draft written up.
FengOffice is used to store images and any documents that do not require real time collaboration such as invoices and client feedback. We use its time tracking and calendar features to make sure we're on task and not running late.
We discovered Catch in the last week and so far it's been working well. We create tasks as new notes and then edit the note to update the task's information or progress. I'm also experimenting with using it to write/research blog posts (this blog post was actually written as a first draft in Catch!) I'll write a bit more about this setup later.