Haven't checked on most links in a while, I just hoard them.
[Lain / cyberpunk messageboard] systemspace.link/
[Pretty dead ancient tier textboard] 4-ch.net/4ch
[Relatively active textboard originally based on a VN called VA-11
Hall-A] dangeru.us/
[Some kind of lainchan spinoff that I don't remember the story for]
arisuchan.jp/
[Imageboard with only a few posts per day but not entirely dead]
sushigirl.us/
[Run of the mill imageboard but you can see anons type out posts in real
time. Decently active] doushio.com/moe/
[Another imageboard using the same script as doushio. Also active]
meguca.org/
[Yet another imageboard using the real time script, but this one is only
available at certain times during the day. It's active but seems to be
populated by only a few users that all know each other.]
chakai.org/tea/
[Simple text based board, very chill]
afternoon.dynu.com/letterbox.html
[Text board based on random threads] pown.it/
[List of sorted active boards about programming and usual internet biz]
4x13.net/list/
[Catalog of somewhat active "2ch style" boards] txtchan.org/
[Relatively active board about bizarre subjects] 4taba.net/
[Kosher friendly board] chan.org.il
[Old /v/ offshoot for some TF2 clan]
boards.fightingamphibians.org/
[Old messageboard dedicated to "cracky"] 195.242.99.71/
[Dead anime message board] desuchan.moe/
[Single category forum with lots of posts, still active]
forum.desync.com/cgi-bin/gforum.cgi
[Fanfic forum about the smurfs...]
bluebuddies.com/cgi-bin/ultimatebb.cgi?ubb=forum;f=1;hardset=0;start_point=0;DaysPrune=0
[Dedicated to the old Habbo raiders] nigrachan.org/