These are imageboards and sites I quite like that feature interesting content or just a nice community.
lainchan
danger/u/
cyberpunkforums
ArisuChan long gone already but still a source of a lot of interesting information
ithinksw possibly an arg, no clue where it leads origin was from mebious which linked to a site called tachibana(dead) which linked to this.
ynoproject a project hosting servers for multiplayer Yume Nikki and Yume Nikki inspired games like Yume 2kki and .flow and a lot more.
sapiensanonym blog on DIY body modification and transhumanism, WARNING: medical topics and blood
powdertoy an impressive physics simulation, ability to simulate a nuclear reactor. A very cool tool.
websdr online radio tool, some
more links :)