The folks in Redmond have been busy the last week. SharePoint 2010 went RTM a couple of weeks ago and showed up for download on MSDN last week. The Office 2010 clients are available now too. If that weren't enough, I saw today that you can download SQL 2008 R2 RTM now. When you install it the build number will be 10.50.1600. The download is a trial. However, the trial is for 180 days, which will be plenty of time for any SharePoint 2010 demos that anyone is setting up. Also, during the install there is an option to put in a license key, so I am guessing it can be upgraded later.
If you're going to be doing anything with SharePoint 2010 and Reporting Services, or some other Business Intelligence features you need SQL 2008 R2.