With Twitter being one of the more popular social networks in Japan, it's a good way to keep up with your favourite mangaka. Some recommendations:
Kengo Hanazawa (https://twitter.com/hanamanko)
The newest artists to pop up on my radar, I wrote about I Am A Hero the other day. And his previous manga, Boys On The Run, received a bit of attention and a movie adaptation.
Takehiko Inoue (https://twitter.com/inouetake)
Definitely one of the highest profile mangaka on Twitter. His art is amazing, and he always has so many different projects on the go. Vagabond is a behemoth that I would love to start reading, but with 34 volumes and counting, it's not going to happen soon. Also popular for his basketball themed Slam Dunk and Real. Real is probably my favourite manga series of all time, and I'm not even interested in basketball.
Inio Asano (https://twitter.com/asano_inio)
Asano is my favourite mangaka. His art is amazing, characters are so well drawn, against some breathtaking inner city backdrops. He writes a lot of small 1-2 volume stories. Solanin was turned into a movie a few years ago. I'm not sure how to describe his current series, Oyasumi Pun Pun. I was very enchanted by the story, setting, and characters when I started, but when you are dealing honestly, bluntly with the topic of awkward teenage boy sexual maturity, things can get... awkward, especially when the main character is also a bird in a human world.