Microsoft has made available six free templates for Office 2007 and Office 2008 (for Mac) with 9 color options. If you are using the latest version of Office suite, you can download the templates for free. The best feature of these designs are that each of them have templates for presentations, spreadsheets, invoices, letterheads, business cards, email blasts, and newsletters.
There are six designs available now, once you select the design, you can chose from nine different colors and then click on the download template button. These templates are zip files and you can use them directly. The templates are of new file formats (.docx, xlsx etc), so they wont open in older versions of Office.
If you are using Office 2007, then you should be definitely checking out these templates.