http://www.musicindiaonline.com/
http://bollyfm.net/temp/
http://hamraaz.org/
http://www.timesofmusic.com/
http://www.sanatansociety.com/Indian_music_mantras.htm
http://www.dishant.com/index1.php3
http://www.earthmusic.net/
http://www.indianscreen.com/
http://www.musicdesi.com/
http://www.hindiranks.com/categoryrank.cfm?Cat=music
http://www.onesmartclick.com/desi/desi-masala.html
http://www.silchar.com/misc/download_hindi_movies.html
mp3 listing 1: http://www.desitorrents.com/forums/forumdisplay.php?f=44 : You need to use a bit torrent software but you get lots of hindi mp3 here.
http://www.geocities.com/Hollywood/Academy/9686/mp3.html : Slow and some links dont work. But lots of hindi mp3 songs.
http://www-db.stanford.edu/~usriv/passions/music.htm : One more personal website providing some mp3 downloads.
http://www.indianscreen.com/songs.htm
mp3 listing 2: One paid site which allows users to download a nice collection of hindi mp3 songs is : www.bollygrounds.com
mp3 listing 3: One great way of downloading hindi mp3 and hindi music is from IRC channels. You need to find out about the legal stuff before you decide to download from there. You need to have an irc chat software for that. You can download mric from http://www.mirc.com
One very popular room is #DESI-MP3 on server IrcSuper.net . Just join the room and you can search and download the best quality hindi mp3 available on the internet. There are quite a few rooms like this. Though not as simple as just clicking and downloading, but this is the best you can get as far as hindi music is concerned.
On joining any room, check for the triggers which tell you what files are available for download.