Are there any anime...
 

that's similiar to Welcome to the NHK that I might enjoy?

NHK is pretty unique, but is there some aspect about it that you're particularly looking for? The emphasis on hikikomori? The psychological issues that the characters face?

Two shows with similarly aged characters that you might try are Eden of the East and Yojōhan Shinwa Taikei ("Tatami Galaxy"). For shows with a strong psychological focus you might take a look at Kuuchuu Buranko ("Trapeze") and Ghost Hound.

Yeah, it's going to be pretty hard to find something like NHK, I was just wondering if there are any more anime that kind of focus on a hikiomori

Chaos;Head and the currently airing Sasami-san@Ganbaranai has the shut-in thing you're looking for.

Really? Chaos-Head?

I'd go for Tatami Galaxy.

Looks quite interesting, I'll definitely check it out

Please check the summary and watch the first few episodes for yourself before deciding. But I'll admit the visual novel (which the anime was based from) was quite good and I heard it was pretty heavy in psychological mess-up. Another thing is that it was made by the same company that bought you Steins;Gate.

if you like the dark humor in nhk then try out Sayonara Zetsubou sensei
http://myanimelist.net/anime/2605/Sa...etsubou_Sensei

I'll second tatami galaxy.

Also check out genshiken.

Yea the visual novel i felt was really good (you can get an english translated version if you need to) but the anime...started good then botched it heavily IMO