Hikaru no Go Vol 19: I always have mixed feelings about this series, since it reads so quickly with all the "action scenes" of Go games being played, but the artwork is so nice and there's always just enough story development to keep me wondering what will happen next. In this volume, Hikaru starts holding a fan like Sai (who is still nowhere to be seen), and there's a great side story about Hikaru's female classmate Akari.
Hikaru no Go Vol 20: I was interested enough to start the next volume right away, which is mostly filled with qualifying games for the Young Lions tournament, including a great cliffhanger match with a cool Korean player. I really enjoyed the scenes where Akira and Hikaru both have matches with their teachers, but at the same time I'm really ready to finish this series since it's so close to the end!
Nana Vol 10: Even though the story is jumping all over the place (since the two Nanas are no longer together), it's amazing to me how well the characters are being juggled, making this manga so much fun to read. Most of this volume is about media scandals concerning Ren and Nana (affecting both Trapnest and the Black Stones), but there's also a semi-cute scene with Takumi and Nana picking out baby shoes.
Honey & Clover Vol 5: The students' graduation projects (including Takemoto's crazy Tower of Youth) are finished in this volume, and Morita returns to Japan after winning a Hollywood award for special effects (which amazes everyone). Yamada makes a nice speech about unrequited love, so it's no surprise that I get more and into these characters with each volume I read!
Mahoromatic Vol 4: I never really intended on reading this whole series, but I guess I'm hooked, and this volume has a cool subplot that wasn't in the anime. Mahoro goes undercover and enrolls as a student at a different school so she can defuse hidden bombs, interspersed with tons of cute and racy scenes (including a crazy bout with a breast enlarger device).