Here are some links to forums and mods for GR
GR.net also has a forum section for other tactical games including Raven Shield.
I'm currently running GR Gold with HX5:Red Sun & Alpha Mod v2.5. AM came with a Standard Upgrade of models for GR so I use that too. Also have the Frostbie mod for winter combat.
Good forum and mod site is 10-David.
2 general sim/tactical sites are SimHQ and Tactical Gamer, both of which have game reviews and forums covering many different games.