Four places I've used them to good effect...
1. On the motherboard mounting posts in my computer music server. Cleaned up hash top-to-bottom.
2. On the mounting posts for circuit boards. Same effect as above.
3. On various parts of base of my ET-2.5 tonearm, such as the cueing lever & the VTA Adjustment lever holder.
4. Best one... around a nude Vishay resistor. Warmed that puppy right up!
Of course, if you've moved up to the newer dampers, the Hal-O's make good interconnect, RCA plug, speaker cable, & power cord dampers too. Effect is not as dramatic there (in my system) as on tubes, but still worthwhile.
I see they are still available on the page for these dampers.
Greg in Mississippi
P.S. Trying to damp circuit boards & motherboards was one of the few times I've achieved 'over-damping'. Having the damping pads on the posts AND additional ones wedged under the boards (or felt under the boards as AltaVistaAudio does on their Counterpoint mods) made the sound dull and slow-sounding. Just use the damping pads on the posts.