Isn't it great, you suddenly have THE idea, the one that will change the world, or at least your financial situation :-)

But besides having that idea, creating and delivering it you will also have to organize, structure, create/find/share information, collaborate... and preferably in a cost effective way (free) Here I'll give you some ideas and tools to accomplish this. All the tools are based on collaboration and sharing over the internet so your partners in crime can even be on different continents and these tools are not only for technical projects.

Structure

First of all you'll need to structure the files and information you'll be creating and gathering.... This will help you find the documents and keep a clear overview of the information. Here is an example structure, feel free to create your own:

00 Initiate
01 Requirements
02 Application
     01 Design
          Graphics
     02 Test
     03 Manuals
     04 Operations
          Setup Client
          Setup Server
03 Data
...........

Tools

Organization
This means structuring the execution of the project, todo lists, milestones, discussions, responsibilities... Checkout Basecamp, they have several plans including a free one to handle 1 project.

Sharing
To easily share your files I propose Microsoft Live Mesh, it allows you to sync files between your pc's, your online Live Mesh Desktop and with other people using Live Mesh. Think of it as syncing your files in the cloud. You just have to install the client, tell it which folders to sync and you're ready. Just work on your files locally and when you save them they will automatically get synced with the cloud and with the people that have access. It works on Windows, Windows Mobile and Mac. Even if you're working alone on this project I would suggest using this tool, you automatically have a backup and you can reach your files from any pc with an internet connection. The only thing it doesn't do is keep a history of your files so you can't retrieve an older version of your document, for that you'll need the the tools from the following section...

Versioning
If you want to keep track of previous versions of your documents (code, graphics,...) you'll need a versioning tool. Most free solutions are based on Subversion, this is an open source source-control system. This is a bit more technical to implement but not to difficult. You'll need a hosting company for your repository and one or two client applications.
XP-Dev has several plans to host your repository including a free one. Once this is set up you'll need an application to retrieve and commit changes from and to your repository. TortoiseSVN is a free tool that integrates with the file explorer and if you're using Visual Studio to do the coding you can use AnkhSVN to integrate with the IDE.

Information
In the course of the project you will probably also do a lot of research and information gathering. This will not always happen in a structured way, you'll want to gather the information first, analyze it and then maybe give it some structure. THE tool for this is Evernote, it runs on every platform and it has a handy browser plugin that allows you to store chunks of information from a website directly in your Evernote notebook. If you use it on your PDA you can take pictures with it and when it gets synced to your notebook it also gets indexed with OCR.

Motivation

Now comes the most important part, delivering the actual project. This might sound easy in the beginning but after a few weeks or months you might get a bit demotivated, distracted with other things. Basically you lost your motivation, this can easily happen when you're working alone on the project. In a group this will happen less likely because you keep each other accountable for the progress and result, of course working with other people (friends, family...) will have other impacts or difficulties on the project but those are outside the scope of this article.

If you're doing it on yourself try to find somebody that will keep you accountable. Also try to use that person as a mentor, someone who has an opinion and ideas. Don't ask somebody who is too nice, it needs to be somebody who will chase you if you don't deliver.

Another way is to promote your product/service when it's still in its concept or development stage. Write blog about your progress, twitter and facebook it. Don't be affraid to share your ideas and progress. This might create a community from which you can get fresh ideas and input from possible clients. This will also make you accountable to the whole internet :-)