Madison Taylor
Sakura's #1 friend! They were best friends, ever since 3rd grade (?). Madison and Sakura care about each other, as best friends should. Madison is always with Sakura on card capturing, making her feel a little better knowing that she isn't alone.
Li Showron
Well, they first started out as rivals, but as time wore on, they became partners in capturing the cards, and then even became friends! In the new season of the Star Cards, it seems that Li has finally developed a full time crush on Sakura.
Meilin Rae
They also just started out as rivals... but their friendship took a while longer to establish. Meilin was very competitive against Sakura, but Sakura always refused to try and have a contest. Meilin saw how nice Sakura was, and they became good friends.
Keroberos
However much Kero shouts at Sakura, he is one of her best friends and will try to prevent anything from happening to Sakura. Kero is always defending Sakura when Yue tries to degrade her. Sakura also seeks comfort in Kero, especially when she's scared.
Nikki, Chelsea, Rita, Zachary
This is pretty much Sakura's gang of friends! However, these 4 aren't as close to Sakura as the rest, as they aren't aware of Sakura's card captor adventures. They're still good friends! Sakura has a knack of always believing the stories that Nikki and Zachary make up...