The beta of SharePoint 2010 and Office 2010 is available on MSDN and TechNet!
The build number for the beta is 14.0.4536.1000 and can be downloaded since 16-11-2009.
If you're having trouble activating the products go to, Start -> Control Panel -> Programs and Features, select the product from the list and click on " Change". This opens up the installer window which has an option to enter the productkey. Do this and click next a couple of times and you're ready to activate :-)
Have fun testing!
Update: here's the public link
http://officebeta.microsoft.com/en-us/products/microsoft-office-2010-suites-comparison-FX101745464.aspx