The definition for what counts as a Domain Specific Language is vague enough to include pretty much anything that's not a general-purpose programming language (e.g. Java) or a modeling language (e.g. UML). For example, the configuration file syntax for Apache HTTPD server are a DSL and the "BB Code" you format these posts on JavaRanch is a DSL.
Lasse's right - XML, ant, even make files have been used as examples of a DSL. In some of his talks, Neal Ford even uses StarBuck's as a DSL because the words "Venti, half-caf no foam latte with whip" tell the barista what ingredients to use and how big to make it. If you're interested, here's a link to an article of his about building DSLs - it's for C#, but you may find it worth reading anyway: http://www.code-magazine.com/Article.aspx?quickid=0902041.
SCJP, SCJD, SCEA 5 "Any sufficiently analyzed magic is indistinguishable from science!" Agatha Heterodyne (Girl Genius)