There are two powerful sample web projects built into VS2K5 whch provide a head start toward building two common types of applications. By release, there may be more such samples. These two samples are an Intranet 'portal' site and an Internet site. The main difference between these two sites is their target audience -- internal users versus anybody on the 'net.
The Intranet Portal is a great application to use to get up to speed with how to build sites with ASP.NET 2.0. It includes support for master pages, a sitemap file, web parts, some security controls, and a bunch of web controls. Web parts in particular are an awesome way to provide users with customization options. Writing about them doesn't do them justice -- if you haven't seen them you really have to try them out to believe how cool they are. Using web parts, users can customize the layout of the page to suit them, using a drag-and-drop interface. The user literally just clicks a link to 'customize page' and from there they can drag controls from one column or header or section to another. Controls can be deleted or added from a 'catalog' as well. When they're done, they just click another link to finish customizing the page, and from that point on whenever they come back, the page will be as they left it.
The Site Map file bears mentioning simply because I think almost all ASP.NET 2.0 developers will end up using this. It can be used along with the SiteMapDataSource control to bind site navigation data to controls like the TreeView or the SiteMapPath (breadcrumb) control, allowing for easy navigation updates.
The Internet site is very similar to the Intranet site except that instead of relying on windows authentication, it has support for authentication using forms authentication. It also has a photo album built into it and some reports for site counters. Naturally the authentication pieces use the new built-in security web controls, and everything is tied into the membership provider by default. The site also uses standard features like master pages and sitemap files to good effect. It's a great starting point for an Internet site, or a great way to learn how to use many of the new tools and techniques available in ASP.NET 2.0.