Microsoft Office can works on Ubuntu, with Wine (Windows 'Emulator' for Linux) which is still in beta. But, it is not stable enough.
If you are looking for stable version of emulator, I recommend CrossOver. CrossOver is a software for Linux and Mac, which allow several famous Windows, eg Office 03,07, to work flawlessly at Ubuntu platform.
CrossOver comes in simple GUI, and you can install CrossOver easily if you're already familiar with how to install software on Linux. You can always google steps if you encounter any problem, which has a lot of easily available solution.
CrossOver is a shareware, means you need pay for it. If you don't wish to buy, you can go to www.warez-bb.org and search for it.
To install Office 2007 at Ubuntu, you need Office 2007 installer and CrossOver. First, install CrossOver. Then browse for CrossOver program, and there has step-by-step instruction on how to install Office 2007. Optionally, you can search for CrossTie for Office 2007, which is a file to tell CrossOver how to install Office 2007 (.inf file for Microsoft Windows).
The screenshot should have a dock named docky below there, but I "Windows Dodge" mode it to make windows for viewing bigger. At Mac OS X, the bottom there just specialised for their dock function only.