How to create a portfolio with links to website without buying domainnames

Hello everybody, 

I want to create a portfolio. 

Under references I want to add all my demosites. 

Is it possible to add links on these so when somebody is seeing my portfolio and go to my work/or reference section and he clicks on one of those demosites, then he goes to this site and the site opens. 

Is this possible within github or do I need to buy a domain name for each site?

Kindly regards

Patrick

Just use github pages.  Make a references.html with buttons that are links to your places on github.