RHQ has a powerful grouping feature: you can generate groups of resources (of compatible and mixed type).
When you go to the Browse Resources page, you can get a list of compatible and mixed groups and from the inventory of a group see all members of said group. Setting up a lot of groups is even easier with the cool DynaGroups feature.
But what if you want to know all groups that contain a certain resource? Of course, you can look into each group and check if it is there. But this can get boring with lots of groups.
There is an easier solution to that: go to the inventory page of the resource and scroll down. You will find a section "Groups Containing this Resource":
This section shows the names and types of groups where the resource is in, as well as member count and availability of the group.