I'd recommend :
-flumpool, I love Hoshi ni Negai wo and their new single MW/Natsudive
-L'Arc~en~Ciel, everybody knows them right
-Bump of Chicken, you could try their album orbital period
-BREAKERZ, Their materials are good and catchy like Bambino
-Aqua Timez, I recommend Utau Sarishi Hana or Niji single
-Ken Hirai his voice is lovely, if you love jazz and so on, you should try his music
-Tamaki Hiroshi has some good stuff, try Bridge album and SLOW TIME single. His voice is 'airy'
-DEEN well you could listen to Yume de Aru Youni Single (I know it's uber old but still it's great)
You could download some of those things at blackrose18's awesome
blog