It's interesting to know that Thermae Romae won 3 times this prize in 2008, 2009 and 2010.
The full list of nominees for this year can be seen here.
However, we can review some of them, not all titles have available information:
I Am a Hero by Kengo Hanazawa
"Hideo Suzuki is a thirty-five year old mangaka assistant struggling to be the hero in his own life by breaking back into the lime light with a new serial all the while juggling his relationship with his girlfriend and his own delusions. However, as hard as Hideo may try, the world seems to have a different set of plans for him; sinister and dark machinations that completely overturn his reality as he knows it."
Silver Spoon by Hiroumu Arakawa
Young boy named Yugo Hachiken apparently aspires to live separated from his family. So he took the chance by enrolling to an agriculture school, one which required its students to live at dormitory. He thinks, with his talent in studying, that no problem will arise no matter what kind of school he goes to. But he's proven wrong. Grown up as all-easy-to-get city boy, he is forced to uncover not-too-convenient truth about agricultural life. Enjoy the story of Hachiken, as he trying to keep up with his friends, farmers' heirs who are already accustomed to hardworking farm life.
Getenrou by Ishiguro Masakazu
Strange people live in a building called Getenrou. There’s boys looking for erotica, a space officer, robots...and then a murder happens…? Officer Sakuraba Saeko is following two siblings who hold the key to solving the mystery, and begins an investigation of her own. What her “sloppy” logic clears up is an astonishing truth hidden in Getenrou…
Shōwa Genroku Rakugo Shinjū by Haruko Kumota
There's no info on this one, except that it was also in Kono manga ga Sugoi! ranking, as the second most read manga by female audiences in 2011.
Giga Tokyo Toy Box by Ume
The sequel to Tokyo Toy Box, the original premise goes around Tengawa Taiyô (the sun in Japan), a great (but unrecognized) game creator and the boss of his own development studio (but he's in debt). He then meets a nice young woman, but she comes to turn his loser company.
Takasugi-san-chi no O-Bentou by Nozomi Yanahara
Takasugi Harumi is a 31 year old man, even though he has a collage degree, he is unable to find a job. One day Miya, Harumi's aunt died suddenly. Harumi had a 12 years old daughter, Kururi, and now that her mother's dead, she has no one to rely on. Harumi has to take care of Kururi now but her heart keeps closed. "Obentou", a lunch box, can be the reason to get closer to each other. Each lunch box has feeling, love and heart to it. This is a lovable heartful story.