Here a few links of interesting sites and boards we regularly visit and highly recommend!
Shmups Forum: Probably the biggest english speaking community for Shoot'em Ups. Highscores, Reviews, Trading and general discussions about Shmups are the main topics on this board.
NTSC-uk: A big site all about videogames, with lots of news, articles, reviews and a pretty active retro section.
Racketboy: A cool community mostly about retro gaming. They also have a podcast, an editorial and a small store with neat accessoires for the old systems.
NeoGeoForLife: This board is all about NeoGeo. Nice infos on the systems and always talks about the good old SNK games.
Retro Gamer: Official forum of the UK based print magazine with the same name which is about classic games and hardware.
Arcade Otaku: This board is less about home consoles and more about arcade coin up cabinets. Lots of talk about the different machines and all the nice games that never made it in the home platforms.
Maniac Forum: Official forum of the printmagazin Man!ac. Great board to gather information and get help on all kinds of topics even those unrelated to gaming.
SNESfreaks: As the name suggests this board is all about the Super Nintendo. The community is rather small still but growing stronger every day. Also a very nice review section including many Japanese titles.
neXGam: One of the biggest German communities about videogaming. Good place to trade, buy and sell.
The(G)Forum: One of the oldest and biggest swiss gaming forums on the net. Technically not German but most members do speak it.
Blogs & Sites:
SuperFamicomGuy: Lots of news and infos about the SuperFamicom. With regular updates and many curiosities this blog will keep you well entertained.
Insert Disk 2 (German): Neat blog of a collector with a huge passion for videogames. He has quite a collection and deep knowledge about retro videogames.
Fudoh's Deinterlacing Page: One of the best sites for infos about scaling and deinterlacing devices. Without this page people would probably not even know about the XRGB or many other facts about retro gaming on current gen TVs.
XRGB Wiki: Pretty much all the information on Micomsofts XRGB neatly packed into one nice wiki. If you are not sure weather to get an XRGB or not, this is the place to read up on it.
Neojaponisme: Not about videogames but about Japan. If you are interested in Japan this is one of the best sites out there. Well written and researched articles about different aspects of Japan and its popculture.