DOMXSStest is a set of cases displaying DOM XSS vulnerabilities.  They can be used to test DOM XSS detection tools or browser controls (such as Webkit/Blink's XSSAuditor), for trainings etc.  The pages are available at http://dmitris.github.io/domxsstest/index.html

References:

OWASP "DOM Based XSS" - https://www.owasp.org/index.php/DOM_Based_XSS
OWASP DOM XSS Prevention Cheatsheet - https://www.owasp.org/index.php/DOM_based_XSS_Prevention_Cheat_Sheet
domxsswiki - http://code.google.com/p/domxsswiki/