Cydric

I just happened to find this thread. I have to agree that basically you're looking for manga in the harem genre and it's a bit broad. Here are a few of my own preferences though and I'll admit now that they are in the Shounen/Seinen genre.

1. Amagami SS and Amagami SS+ (the anime goes into the harem better than the manga. The manga is all personal interaction)
2. Sekirei (A bit of censorship depending on where you go. Not a bad story with alot of women with powers)[beware there is a bit of fanservice]
3. Freezing (again, abit of fanservice; you have been warned)
4. Hyakka Ryouran (Samurai Girls) [it's an anime, probably has a manga/light novel but I never looked]
5. Omamori Himari
6. Kiss x Sis (don't say I didn't warn you; this series gets seriously close to the hentai border if you read the manga. the anime is garbage because it only focuses on one point of life where the manga is further into the harem route; again, you've been warned)
7. Maken-ki
8. Macross Frontier (Love triangle following the Robotech series)
9. Sora no Otoshimono
10. Bravo Girls
11. Eiken
12. Princess Lover
13. Rosario Vampire; Rosario Vampire II (the mangas are a great read)
14. They are my Noble Masters
15. Mahou Sensei Negima (I recommend the manga, didn't watch the anime because the first part changes so much of the story)
16. Seitokai no Ichizon (funny, not alot of harem aside from the guy pining for the girls. Moreso comedy but a great anime)
17. Zero no Tsukaima (manga doesn't go far, anime has 4 seasons with 24 episodes each)
18. Onegai Twins (Love triangle, same writers as Onegai Sensei and Ano Natsu de Matteru; anime)
19. Hayate no Gotoku
20. Koisome Momiji
21. Nisekoi
22. To Love-Ru; To Love-Ru Darkness (ecchi shounen comedy; Darkness is similar to Kiss x Sis where it gets dangerously close to the hentai border)

Again, some of them you may not be interested in and I tried to stick to a harem/love triangle theme. If they are recommended then they just fit into the genre and are on my list. I hope you aren't offended with my selections and that you can find something from this that you enjoy. Harem restricts my list so if you want other anime/manga then I can recommend more =)