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.
The latest (3.1.2) I could find was at https://maven.java.net/content/repositories/releases/org/glassfish/main/extras/glassfish-embedded-all/
Unfortunately, for 126.96.36.199 as of August 21, 2012 seems to be nowhere!
I've just opened an issue: http://java.net/jira/browse/GLASSFISH-19028 The very strange thing is that while opening the issue I saw the 188.8.131.52 still classified as "Unreleased Version"...
UPDATE! Today glassfish staff answered : 184.108.40.206 maven artifacts are not yet available on maven central / maven.java.net release repo. You can find them here: https://maven.java.net/content/repositories/releases/org/glassfish/main/extras/glassfish-embedded-all/220.127.116.11/
As of August 3, 2011 at 12:43 PM EDT http://download.java.net/maven/glassfish/org/glassfish/extras/glassfish-embedded-all/3.1.1 should get you what you want. This is the correct repository.