It seems that everyone is doing it, so I decided to put together an anime harem of my own. Three of the eight girls below immediately came to mind but it was amusing to browse through my anime list on ANN and pick out five more from the the shows I've seen.
There's two main personality types in here. Akari, Hagumi, Chihiro, and Belldandy are all incredibly sweet, caring, and gentle. On the other hand, Kagami, Kyou, and Mei are all kind of the sarcastic tsundere types. And then there's Horo, who is just all kinds of awesome; she acts so playful and innocent but is actually incredibly intelligent and clever.
Also...
I put together a harem of forbidden lolis because they're just too great. They all have their own little quirks that set them apart and make them oh-so-adorable and funny... Which I don't really feel like going into right now. But if you watch the series they're from you will see. Especially Aria and Kaleido Star.
If you want, you can grab the empty harem template and put together your own.