There are
16 questions tagged powerline-networking
7 with homeplug
6 with ethernet-over-power
powerline-networking and ethernet-over-power should be merged into powerline-networking, I believe – although technically you could run some non-Ethernet layer 2 protocol over a powerline network, I don't think that's available on the market.
homeplug is by far the most popular powerline networking technology (27 hits for the keyword on Super User). It's probably not right to merge with powerline-networking but perhaps it would be good if the homeplug tag wiki also linked to powerline-networking?
Background: Wikipedia page