It depends on the context. You can never find a one word translation for this kind of words.
This word came from Japanese, originally お宅 or 御宅(おたく, pronounced otaku). If you wanna use this word in it's original Japanese meaning, then use "otaku",as hakee suggested, which means social incompetent people, normally obsessed with electronics and Japanese animation, comics, and games(hereinafter ACG). Lately some otakus petitioned to legalize the marriage with ACG characters. The protagonists in the Japanese drama "秋葉原@deep" are stereotype otakus, though exaggerated.
There are words of similar meaning in western culture, "nerd"(more in Britain) and "geek"(more in US), which also mean social incompetent people, sometimes very into electronics, sci-fi, superhero comic and similar hobbies (traditionally US ones, but it's gradually changing by the significant influence of Japanese ACG). Nevertheless, the aforementioned terms "nerd" and "geek" often possess the sense of "weird genius"(at least knowledgeable). Stereotype of nerds and geeks(again, exaggerated) can be found in the sitcoms "the IT crowd" and "big bang theory" respectively.
By the way, I'm one of them.
Obviously my essay is driving me mental...
ex linguis vis
в языках сила
from languages comes strength
des langues vient la puissance
desde los idiomas, el poder