On the following pages you can find more information and some tutorial material from Microsoft.
There is no online training material or tutorials online at the moment for BizTalk 2013. You may check this page
Many of the features available in BizTalk Server 2010 are also applicable to BizTalk Server 2013, so you can also see the following articles:
Nice set of useful links.
thanks for sharing the consolidated list of urls
Its really nice set of links to communicate with rest based endpoints :)