Sometimes the best way to capture all the important variables around a project is to map them out visually. For my money (which is exactly zero dollars), there's no beating XMind. This free mind mapper runs on Windows, Mac, and Linux, and even comes in a cross-platform portable version that you can run from a thumb drive. Once you create a mind map, you can upload it to XMind.net (either publicly or unlisted) to access it from all of your other computers. For $49 a year, you can also add security and collaboration features. (Get XMind)
Hard-core productivity types need no introduction to Evernote. This online capture tool is way more than a note-taking service. You can type in notes, capture pictures from your smartphone camera, clip content from Web pages, and dictate voice notes into Evernote, and then search for them--even for handwritten words on scraps of paper in pictures--when you need them again. (Get Evernote)
Keeping a team on track takes focus. To ensure that everyone is concentrating on a shared project, try Huddle. This Web-based project-management service gives you a workspace and calendar that you can share with your entire group, so you can dole out tasks, share whiteboards for brainstorming, collaborate on documents, and chat about how terribly behind schedule you are. (Get Huddle)
Have an amazing productivity booster I didn't mention here? Tell me about it in the comments and I'll most likely give it a try (if I haven't already).