Howdy all!
I've been using this addon lately and I love it and thought it would be a good one to share with the family. It's called Social Indicators and it puts a little icon next to guild mates in groups and chat, so you can tell who's in your guild wherever you are. I think it's awesome and I've had some surprised guildies when I knew they were in GSCH. It's also actively managed and updated! :)
Here's the link: http://www.esoui.com/downloads/fileinfo.php?id=276
Enjoy!
Rainingblood, AKA Aelfgim Frostborn