http://maven.glassfish.org/content/groups/glassfish/ looks like it should be GlassFish's official Maven repository, but it currently hosts only up to version 3.1.1-b05 of glassfish-embedded-all (see http://maven.glassfish.org/content/groups/glassfish/org/glassfish/extras/glassfish-embedded-all/).
http://download.java.net/maven/glassfish/org/glassfish/extras/ is linked to from Embedded GlassFish's site (Embedded Jars). It doesn't look like an official Maven repository but hosts up to 3.1.1-b11 (at http://download.java.net/maven/glassfish/org/glassfish/extras/glassfish-embedded-all/).
So the question is which would be the reliable repository to get the Maven dependencies for Embedded GlassFish from.