Master pages are the starting point for branding sharePoint sites, There has been quite a changes in the new SharePoint foundation Master Pages.
Firstly it no more HTML Table based layouts, Now the Layouts are based on Div, we could see that by opening the v4.Master page from the following location - %Program Files%\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\GLOBAL
And the second advantage is content placeholders are the same for both Application and Content Pages, which results in consistent Look and Feel across content pages and Application pages.
SharePoint has a default minimal master page for branding. Minimal.Master page can be found at the following location of your SharePoint installation - %Program Files%\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\GLOBAL
Here are some links on Master pages
Default Master Pages in Sharepoint foundation
Upgrading an Existing Master Page to the SharePoint Foundation Master Page
Randy Drisgill's Starter master page
Erik Swenson SharePoint 2010 Base CSS Classes