The Visual Studio 11 Ultimate Beta ISO is a disc image containing everything you need to install Microsoft's latest version of its IDE, complete with simplified interface, new Windows 8 development support (including tools to help you publish directly to the Windows 8 App store), and a host of other productivity improvements, new language features and more.
As usual with Visual Studio, installing it will get you plenty of extras: IIS 7.5 Express, Web Deploy 3.0, Blend, Silverlight, ASP.NET Web Pages, assorted SQL Server 2012 tools, even a beta of .NET 4.5. The package can be installed alongside Visual Studio 2010, though, conveniently. And if you do have problems with any of the new components then they can be uninstalled (though there are so many that it might take you a while).
Installation itself is simple. Burn the image to a DVD or mount it in a virtual drive, launch vs_ultimate.exe and it'll begin the setup process. You'll probably have to reboot once, but after that there's nothing for you to do: just leave the program running until installation is complete (which may take some time, so be patient), then start exploring the new IDE.
But if this doesn't work for you for some reason then betas of Visual Studio Premium, Professional, Test Professional, Express and more are also available, both as ISO files and web installers via the Microsoft site.