Unable to connect to SharePoint site from Visual Studio 2010

You may get message like:
Cannot connect to the SharePoint site: http://localhost/. Make sure that this is a valid URL and the SharePoint site is running on the local computer …

You need to add your currently logged user (under which you run Visual Studio) to the SQL Server users and map it as owner for following databases (obs names maybe not exact):
SharePoint_Config
SharePoint_AdminContent_[guid]
SharePoint Site Content DB

More about this issue can be found:
http://www.sharemuch.com/2010/03/19/resolving-vs-2010-solution-deployment-issues-for-sharepoint-2010-projects/