If you liked the K-On! manga, the Anime-Planet community thinks you'd like:
Miss Yukari's high school class is far from average. With ten-year-old genius Chiyo; dim-witted ‘Osaka'; weight conscious Yomi; loud-mouthed and energetic Tomo; and the ultra cool, animal-loving Sakaki, daily life is far from dull. Follow the day-to-day lives of this fun-loving group of girls as they progress through high school. From annual cultural festivals to gambling, from first dreams of the New Year to death-defying road trips, the lives of these students and their teachers are always exciting and new.
Both Azumanga Daioh and K-ON! are 4-panel comedy manga. they both share the same sort of style of comedy, and are relatively slice of life. If you enjoyed one then it is worth checking out the other.
Azumanga Daioh and K-ON! are both 4-koma series' that focus on a group of high school girls in their daily lives - whilst Azumanga can be a bit wackier and K-ON! can rely too heavily on moe at times, you're bound to enjoy one if you're a fan of the other.
In present day Japan, the life of a school girl is never dull. The easily-bored Konata never finds time to study because of her otaku habits, which frustrates hard-working Kagami to no end. On the other hand, laid-back Tsukasa always manages to go with the flow, while Miyuki is concerned with keeping her status as resident know-it-all. Join these four girls as they muse and meander their way through everyday events such as eating chocolate cones, doing homework, gaming, and trips to the beach galore.
Lucky Star is one of the animes where real life situations can be funny. Join the wacky adventures of these high-school girls! You'll be nodding your head saying "Ah~ I've been through this"
Enter K-On! This is another slice of life comedy that come about in 2008. [i think, about its release part] Funny at every page, it's hard not to stop laughing to breathe.
If you enjoyed one, check the other out!
Lucky Star and K-On! share the same kind of charm. They both revolve around groups of girls that hardly get any work done, like studying (or trying to, anyway) for tests or talking about nonsensical things. Both are very moe.
Yamabuki High School attracts many art students due to its special art classes. Among the school's new pupils is Yuno, who dreams of becoming a famous artist. She lives in the nearby apartment complex Hidamari-so, along with the hyperactive classmate Miyako, the weight-obsessed Hiro and the tomboyish Sae. Together, the students live their day to day lives, including investigating the school's bizarre myths and deal with their cosplaying teacher. But whether they are in school, at the apartment or out shopping, working or playing, the four friends always manage to have fun in the process!
Hidamari Sketch is cut from the same cloth as K-On!. These two manga share the same tone, approach to their ostensible subject material (Hidamari is as much about art as K-On! is about music), and an occasional character (just like Sawa-chan-sensei, Hidamari's featured homeroom teacher, Yoshinoya has a penchant for cosplay and is a total flake). While the girls at Yamabuki are slightly more functional than the Sakura High Light Music club, they are just as silly. If you giggled through K-On!, Hidamari Sketch will surely get some laughs out of you.
As mentioned in the above recommendation, these two are very much alike in plot (if you can call it that). I do find that K-On! focuses more on the characters in their club, while Hidimari Sketch focuses more on the characters off campus. I find the humor in both mangas to be especially similar, including the teacher's role, pun timings, character types, and the occasional obligatory yuri references.
Both Boku wa Tomodachi ga Sukunai and K-On are manga based around a really slack highschool club. They both tend to get very off track with club activities so members mostly hangout or end up doing random activities. Yozora and Mio are also very similar, mostly in looks, but in shyness as well. Fans of one would enjoy the other.
Ayumi, Kei, Koyoi, Rika and Nao are five middle school friends whose hot topic of conversation is, as always, love. Ayumi dreams of having a boy confess to her and can't understand the idea that receiving unwanted confessions can be troublesome. She even believes that she will happily accept any guy who approaches her - that is, until she receives a love letter from Misao, a large, delinquent high school boy whose very presence makes small children cry! Not wanting to date him but too scared to reject him, Ayumi has no idea what to do, especially when Misao, now nicknamed Beast-kun by the girls, begins following her to and from school. To make matters worse, Ayumi then falls for Mamoru, a boy in her class who is Beast-kun's brother! With plenty of experiences in life and love left ahead, will the girls retain their naive beliefs, or is it time to shake off that brother complex and realize that appearances aren't everything?
Both of these manga focus on young school girls and their day to day lives. While K-ON! focuses o the light music club and Hatsukoi focuses on the girl's love lives both share a similar comedy style that is generally more gentle than wacky.