[Kotohono]

Toradora, it has 3 lead girls but I wouldn't call it a harem, it's a very good romance series.

Kobato it's a bit slow on the romance, but it's an enjoyably series with a good ending.

If you're ok with omnibus instead of harem[ie each girl gets an "arc"/"route"], then Amagami SS is worth checking out.

Also maybe Otome Youkai Zakuro and Spice and Wolf.