Switch Girl by AIDA Natsumi the only bad thing is that it is an ongoing manga and not completely scanlated. It kinda reminds me of Kare Kano... I also think the manga Power!! also known as Girl Got Game by SEINO Shizuru is hilarious .I know I have read more but I just can't think of them right now. If I think of anything else I will try to post it lol
Carat! - Obscure crack magical girl manga. ...and um, a magical boy. omgidek Hana ni Arashi - Love story between a super-powered girl who just wants to be normal and a super rich heir ("If you ignore my personality, I'm perfect!")
Yanki to Megane-chan is defs funny, but is shounen.
Kanoko/Ai Dano is really good, but I wouldn't say it's funny. At least not compared to NG Life (arrgghh, I was so rooting for Yuuma, too). Daisy is very good and hilarious... But a little tiring to read, for some reason. I only read VB for the art. I don't find it funny.
The funniest I've read by far is Fujoshi Kanojo, a shoujo based on real experience, but that's huuugely garnered for BL/yaoi fans. It's boy-girl, but... Try it, if you'd like. If you like NG Life, you might like this. Just warning you of the dangers of the "rotten" world.
You might like Oreimo, but that's harem and only the anime and light novel are good (and I mean really good). But where else will you read a girl make her brother go out and buy siscon 18+ eroge for her?
Watch out for Shizuru Seino's stuff. It tends to be overly ridiculous--interesting, but a bit too much.