generalized soft-forks:
http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-December/012073.html

bip102 forced soft-fork:
http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-December/012153.html

auxiliary blocks and evil soft-forks or forced soft-forks:
https://bitcointalk.org/index.php?topic=283746.0
https://bitcointalk.org/index.php?topic=874313.0

soft-fork block size increase using extension blocks:
http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-May/008356.html

extension blocks were also discussed in this interview:
http://diyhpl.us/wiki/transcripts/bitcoin-sidechains-unchained-epicenter-adam3us-gmaxwell/
.... which includes something very similar to the idea of a soft-hard fork (something I was informed about on 2015-06-13 ..... not sure if I should mention this?)

some discussion from today re: origin of the term evil fork, evil soft-fork, forced soft-fork:
https://www.reddit.com/r/Bitcoin/comments/3yrsxt/bitcoindev_an_implementation_of_bip102_as_a/cyg2g7q

some much older discussion about extension blocks and sidechains:
http://gnusha.org/bitcoin-wizards/2015-01-01.log

some discussion about "generalized soft-forks" and extension blocks and evil soft-forks:
http://gnusha.org/bitcoin-wizards/2015-12-20.log

segwit soft-fork makes use of a similar idea:
http://diyhpl.us/wiki/transcripts/scalingbitcoin/hong-kong/segregated-witness-and-its-impact-on-scalability/

discussion about evil forks and evil soft-forks and extension blocks:
http://gnusha.org/bitcoin-wizards/2015-12-30.log

fork types:
http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-December/012172.html

these links are also mentioned here:
https://www.reddit.com/r/Bitcoin/comments/3yrsxt/bitcoindev_an_implementation_of_bip102_as_a/cyg7mdr

and also mentioned here:
http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-December/012173.html