Off the top of my head... (Stuff I enjoy/ed watching)
Ongoing
Bakuretsu Tenshi (Action, Mecha)
Kono Minikuku Mo Utsukushii Sekai (Comedy, Ecchi, Romance, SciFi, Shoujo, Shounen)
Midori No Hibi (Comedy, Ecchi, School)
Naruto (Action, Adventure, Comedy, Magic, Martial Arts, Shounen, Super Power)
Sensei No Ojikan (Comedy, School)
Tenjou Tenge (Action, Comedy, Ecchi, Martial Arts, School, Super Power)
Complete
Ai Yori Aoshi (Comedy, Drama, Ecchi, Romance)
Ai Yori Aoshi Enishi (Comedy, Drama, Ecchi, Romance)
Azumanga Daioh (Comedy, School)
Chobits (Comedy, Ecchi, Romance, SciFi)
Full Metal Panic! (Action, Comedy, Ecchi, Mecha, Romance, School, SciFi)
Full Metal Panic? Fumoffu (Action, Comedy, Ecchi, School)
GetBackers (Action, Comedy, Shounen, Super Power)
Gundam SEED (Action, Drama, Mecha, SciFi)
Gunparade March (Action, Mecha, Romance, School, SciFi)
Gunslinger Girl (Action, Drama, Mystery, SciFi)
Kiddy Grade (Action, Ecchi, Kids, Mecha, SciFi, Super Power)
Kimi Ga Nozomu Eien (Drama, Love Story, Romance)
Mahoromatic (Comedy, Drama, Ecchi, Mecha)
Mahoromatic ~motto utsukushii mono~ (Action, Comedy, Drama, Ecchi, Mecha)
Mahoromatic Summer 2003 TV Special (Comedy)
Noir (Action, Adventure, Drama)
Onegai Teacher (Love Story, Romance, School, SciFi, Space)
Onegai Teacher OVA (Ecchi, Love Story, Romance)
Onegai Twins (Comedy, Drama, Ecchi, Romance, School)
R.O.D -The TV- (Action, SciFi, Super Power)
Scrapped Princess (Action, Drama, Fantasy, Magic, Super Power)
Trigun (Action, Comedy, Drama, SciFi)
Uchuu No Stellvia (Action, Kids, Romance, SciFi, Space)
VanDread (Action, Adventure, Comedy, Ecchi, Mecha, SciFi, Space)
VanDread The Second Stage (Action, Adventure, Comedy, Ecchi, Mecha, SciFi, Space)
X (Action, Fantasy, Magic, Super Power)
You could always go to websites like
AniDB or
AnimeNfo and look around in the genre listings of genres that you like.