You've probably seen animes with parodies catered towards otakus like Lucky Star or Hayate no Gotoku, but there isn't one that fully captures the otaku nature like Genshiken.
Genshiken is all about otakus and their lives. It features a wide cast of the many different types of otakus and their hobbies, so no matter what kind of otaku you are, you will be able to relate closely to the happenings in this anime.
Ohno cosplaying Yoko!
Genshiken is based off a manga series by Shimoku Kio (yes, I wiki'ed it).
The story is simply about a quiet boy named Kanji Sasahara. Secretly a closet otaku, he wounds up joining Genshiken. Along the way, he will meet with the various members of Genshiken; the method chosen to introduce the different kinds of otakus to the audience.
Of course, an otaku series wouldn't be one without an anime to stand as a basis of their interest. Aside of mere mentions of games like CVS2, KOF and FF, Genshiken members watches and constantly mentions an anime named "Kujibiki Unbalance". After the first season of Genshiken was done, Kujibiki Unbalance was eventually created as a 3 part OVA. In 2006, it developed a 12-episode version.
So as we know, Genshiken is mostly about the characters and their reactions to different scenarios placed upon them, rather than the plot. So I'll just give a brief overview on the characters:
Kanji Sasahara: Initially a quiet closet otaku, Kanji eventually came into terms with his otaku nature as he spent more time in Genshiken. Although he has no talent in drawing, he is actually very motivated and plans to become an editor in the future.
Makoto Kousakaa: Kousakaa is your video game fanatic, particularly with ero-games and fighting games (did the author of Genshiken interview arcade regulars or something?). He is considered a 'pretty boy', and is the most upbeat of all the members, as well as the most dense. He has a girlfriend who share no interest in the otaku culture, although he is considered to be in a different level of 'otaku-ness' by most of Genshiken's members
Saki Kasukabe: Saki is Kousakaa's girlfriend and the only non-otaku character in the anime. She is the character that shows what 'normal people' think of otakus and their interests. In many ways, Saki's ignorance towards the otaku culture spices up the whole show. Towards the end, she grew attached to Genshiken and its members, though she still has no interests in doing otaku stuffs.
Harunobu Madarame: Maradame is your very typical hardcore otaku, who will do anything to obtain what he wants. If he caught wind of a rare item being avaliable downtown, he will be there no matter what. He's the kind with the 'Pay first, take damage later' attitude, and he carries it out to a rather alarming degree.
Souichiro Tanaka: Tanaka loves making stuff, be it plamo or cosplay costumes or figmas. He enjoys the culture of cosplay alot.
Mitsunori Kugayama: Kugayama is your artist without motivation. He loves drawing ero stuff and he stutters alot.
Kanako Ohno: Ohno is the first female member of Genshiken. She is an avid cosplayer and thus shares a close connection with Tanaka. Although she's soft spoken, she often attempts to make the other females around her cosplay. She has a fetish for middle aged male characters.
Chika Ogiue: Ogiue is the 2nd artist of Genshiken. She hates her otaku nature, but she ends up joining Genshiken anyway. She often draws yaoi doujinshi (fujoshi). Towards the end, she opens up as she creates her own doujinshi. There's some chemistry between her and Sasahara.
Manabu Kuchiki: Kuchiki is an annoying otaku. He's really annoying. He also loves anything that's cute and often mimics certain anime characters. Deep inside, he's actually a rather nice guy. Put these together and you get one really misunderstood otaku.
Shy Sasahara overcoming his otaku nature
Genshiken currently has 2 seasons and 3 OVAs. I don't know if 'normal people' will understand much of what is going on, but it is a great show for all otakus.