A Coworker just asked me if there was a command to determine which groups an entity was a part of. A quick search of the help did not turn up anything relevant that I could see so here I am to ask all of you.
This API might help, it searches for nodes or elements.
Keep in mind the fact that groups are lists of IDs associated with rules. They are as clean as the user wants them to be. So if you get wierd results with the API, try condensing your groups to be sure.
On the FEMAP "Select" Toolbar, there's an option on the second icon to toggle on/off "Layers/Groups in Tooltips". If you toggle this on, when you are using the Select Toolbar to choose elements, nodes, etc. and you have the tooltips on, you will see Group and Layer information in the tooltip. In addition, if have the "Entity Info" pane open, you will see it there as well.