Definately ignore is best solution. There is nothing you can do to control inbound links
I wouldn't say nothing, these domains are registered to someone and if my rankings suffer while under the effects of a black hat attack I have the right to sue and/or make a criminal complaint. These particular links are blatant and very targeted.
Update: a friend of mine runs a similar site with forum, we became friends because of our sites many years ago, and he contacted me saying he received an email that appeared to be from me requesting that I remove an inbound link since the page would be taken down soon. Obviously that's not true, so this blackhat attack is very targeted.
If you can offer any tips on tracking down the author, and perhaps offer tips on figuring out which site is benefiting from this, I'm all ears. I'm inclined to find out who this is at this point.