For future reference, this post was written at the time that SharePoint 2013 was in Technical Preview.
While working with the SharePoint 2013 technical preview, you may find yourself actually want to develop something :) I wanted to explore developing a workflow for my current client whom is on the RAD MSFT program for SharePoint 2013, so spun up the preview. So, you might be installing Visual Studio 2012 and then install SharePoint 2013, and expect there to be some relevant project templates available for you to develop against. Too bad, no go.
To get em in there, go to here:
Navigate to the Tools section. You will find them there. Shut down Visual Studio, install, you should be good to go. Unless you are trying to use the WWF 4 toolbox items. To get that with targeting to .NET 4.5 add Workflow as a new item, but DO NOT use the Sequential or State Machine workflow since it will go to the .NET 3.0 stack.