Sailormoon has a lot of great songs, they're all pretty poppy and have a younger audience appeal. My favorites are Sailor Star Song (the theme song for the last season), Rashiku Ikimashou (one of the third season ending songs) and Ai no Senshi (second season battle song). The Sailormoon musicals (also known as Sera Myu) have some awesome stuff, particularily Traditional the Grace and Galaxia Gorgeous.

Cowboy Bebop and Evangelion have some kickin music too. Yoroiden Samurai Troopers (Ronin Warriors) also has an awesome soundtrack. FLCL's just rocks (I love the Pillows), and the theme song for Azumanga Daioh is awesome and very funny. Devil Hunter Yohko has a great opening/ending theme and a lot of awesome image songs.

Anyone ever listen to Animetal or Parapara? Animetal and Animetal Lady does awesome rock remixes of anime themes (mostly older series). My faves are Moonlight Densetsu (Sailormoon) and Dare Da (Gatchaman). Parapara is more of a dance remix deal, they do an awesome cover of Stardust Eyes (Yoroiden Samurai Troopers).

Whew. I guess that listening to anime music for 10 years gives me a lot to talk about.