You don't need two separate VMs to create the farm, although you will still select the "Complete" option in the wizard when installing SharePoint. I'm right in the middle of doing the exact same thing with VMWare Workstation 7 and am going to post a blog here later today:
http://www.codersbarn.com/post/2009/11/21/Install-SharePoint-2010-on-Windows-2008.aspx
You don't need AD on a dev machine either. You can get around the "no local account" restriction with SharePoint 2010 by following these steps:
http://sharepoint.microsoft.com/blogs/fromthefield/Lists/Posts/Post.aspx?ID=112
I'm using W2K8 Standard - as far as I can recall there is some new hotfix for R2, so check the team blog.
Some links for the DB part:
Script to open SQL Server ports:
http://support.microsoft.com/default.aspx/kb/968872
SQL Server 2008 SP1:
http://www.microsoft.com/downloads/details.aspx?familyid=66AB3DBB-BF3E-4F46-9559-CCC6A4F9DC19&displaylang=en
CU2 for SP1:
http://support.microsoft.com/kb/970315
EDIT
If the SP Pre-Requisites checker fails regarding Powershell, just install the latest 2.0 version manually:
http://www.microsoft.com/downloads/details.aspx?FamilyId=d37e25cf-db05-4b23-a852-cdf865d81b82&displaylang=en
EDIT
Fix for R2:
KB976462 would be the WCF Fix article for Windows 2008 R2 and Windows 7
http://support.microsoft.com/kb/976462 (link not activated yet)
http://go.microsoft.com/fwlink/?LinkID=166231 (this is the download)
EDIT
http://andreasglaser.net/post/2009/11/17/Installing-SharePoint-Server-2010-on-Windows-Server-2008-R2-and-SQL-Server-2008-R2-Part-4-Active-Directory-installation-and-configuration.aspx
http://andreasglaser.net/post/2009/11/17/Installing-SharePoint-Server-2010-on-Windows-Server-2008-R2-and-SQL-Server-2008-R2-Part-1-Overview.aspx