Off the top of my head, in no particular order at all.
Probably post again when i think of what I missed out.
Openings:
Porno Graffitti - Mellissa (Full Metal Alchemist)
L'Arc En Ciel - Ready Steady Go! (Full Metal Alchemist)
Hitomi - I Am (Inuyasha)
Nanase Aikawa - Owari Nai Yume (Inuyasha)
Every Little Thing - Grip! (Inuyasha)
Minami Kuribayashi - Precious Memories (Kimi Ga Nozomu Eien)
Under 17 - Love Slave (DearS)
Megumi Hayashibara - Sakura Saku (Love Hina)
Ichiko - Kio No Mahou (Maburaho)
Under 17 - Mouse Chu Mouse (Mouse)
Ali Project - kopperia no Hitsugi (Noir)
KOTOKO - Shooting Star (Onegai Teacher)
Youko Ishida - White Destiny (Pretear)
Hound Dog - rocks (Naruto)
Asian Kung Fu Generation - Haruka Kanata (Naruto)
Tasuku - Little By Little (Naruto)
Flow - Go!!! (Naruto)
Steve Conte - Stray! (Wolf's Rain)
Okui Masami - Shuffle (Yu-Gi-Oh!)
Kimeru - Overlap (Yu-Gi-Oh!)
Coorie - Melody (Midori No Hibi)
???? - Ai (Excel Saga)
The Scanty - I Love U (Full Moon Wo Sagashite)
The Scanty - Rock N Roll Princess (Full Moon Wo Sagashite)
Mikuni Shimokawa - Tomorrow (Full Metal Panic)
Round Table - New World (.hack//DUSK)
BOA - Duvet (Serial Experiments Lain)
Round Table - Let Me Be With You (Chobits)
Endings
Rei Tanaka (Ningyo Hime (Chobits)
Nana Kitade - Kesenai Tsumi (Full Metal Alchemist)
Do As Infinity - Fukai Mori (Inuyasha)
Ayumi Hamasaki - Dearest (Inuyasha)
???? - Rumbling Heats (Kimi Ga Nozomu Eien)
Kirika - canta Per Me (Noir)
Yoshida Sayuri - Lucky Star (Pretear)
Akeboshi - Wind (Naruto)
Masu Misairu - Ima Made Nando Mo (Naruto)
TiA - Ryuusei (Naruto)
Okui Masami - Ano Hi No Gogo (Yu-Gi-Oh!)
CAVE - Rakuen (Yu-Gi-Oh!)