Here you will find links to various websites with Islamic music. There is a difference of opinion among the scholars about what kind of music is halal. To learn more about various Islamic opinions, visit: Fiqh of Music page, which contains a brief summary of the Islamic regulations about music and a message to young Muslims. You may also want to check out nasheed videos at YouTube.com (RSS).
Anasheed.com - A growing site featuring nasheeds in various languages. Appears to be most or all halal nashids.
Islamic Audiophiles - Collection of Islamic audio resources including naats (recitations about the Prophet sAas).
Islamic Broadcasting Network - Online radio station broadcasting Quran, hadiths, nasheeds, khutbas, and other Islamic programming. Good to listen to all day, mashallah.
Islamic Nashids - Nasheeds about the struggle in the path of Allah.
Islamified - Islamic hip-hop MP3s from various artists.
Junoon - Pakistani rock band. Uses musical instruments.
MYNA Raps - A rap group founded by Muslim Youth of North America. Uses synthesized percussion but no wind or string instruments.
Mountain of Light - Official website for Yusuf Islam's record company; features Yusuf Islam, Zain Bhika and more. Note: There do not appear to be any samples you can listen to, but you can order CDs here.
RadioIslam.com - Features Dawud Wharnsby Ali, Nojoum and more.
Soldiers of Allah - A rap/hiphop group of "da'wah-carriers" for the cause of Allah SWT.
Sons of Hagar - A Muslim rap group. Uses musical instruments.
Telagabiru - Official website for Telagabiru (Blue Well), a Malaysian record company; features Hijjaz, Saujana and more. Artists use Malaysian percussion instruments. Site is in Malaysian.
Upright Song - Songs from Mustaqiim Sahir's album. Completely halal nasheeds (voice only).
Note: You will need the Real Audio Player to listen to most of the songs at these sites. You can download it from Real Networks.