Merge Computers?

I have 2 computers, an iMac and a Macbook Pro.

I have done a clean install on both of them, but it would be much easier for me to be able to have it where whenever I make a change on my desktop, my laptop is changed too, and vice versa.

Is there any way that I can update the 2 computers whenever I want so that it updates my laptop when I make a change to my desktop? I can't think of a good way to explain what I mean, but here is basically what I want to happen:

1. I turn on my iMac and make a document with Pages, download some music with iTunes, and play and save a game of Half-life with Crossover.
2. I turn on my Laptop, and it automatically retrieves all the changes from my desktop, and downloads the document, music, and the game file.
3. Still on my laptop, I delete an application, download a PDF, and change my desktop.
4. I go back to my desktop, and it automatically deletes the application, downloads the PDF, and changes the desktop.

That is sort of what I want to be able to happen, not exactly like that, but you get the idea. Any help?

EDIT: Preferably something that doesn't cost cash.

 

Well I would like something that doesn't cost cash. Something similar to home-sharing in itunes, except the whole computer.