By kumodot New MaxScript. Simple and handy as aways. Free.
It's very useful for my use. You can quickly save and recall up to 5 groups of selections. You can increment memories adding objects to them (Which is SO useful in some situations (to help in the process of organizing big and messy scenes)...
Hide and Un-Hide from Memory buttons. Isolate groups, etc.
BTW, the video says QuickSelect, but i changed the script name to Memento.;)