Was Tomoyo in love with Sakura?
On the TV Tropes page, Tomoyo is listed as a Token Yuri Girl:


  Tomoyo Daidouji in Card Captor Sakura, though it was toned down a bit in the anime. The manga actually had her telling Sakura that she loves her in that way, though it went right over the heroine's head. 


So it seems that it's toned down in the anime (I didn't seem like anything other than best friends and maybe borderline infatuation in the anime), but blatant in the manga. Also noted in the CSS wiki:


  While Tomoyo is in love with Sakura, she notes that she is happy to be able to be with Sakura and does not require Sakura to love her back. 


According to this blog post (contains lots of other instances), it happened in Volume 2, Chapter 2: