Songza.com : This is a funky search engine for songs and an internet jukebox. Its spiders search a lot of music websites including even youtube, google video etc. Though it isn’t only for Hindi songs, you can try to find out the songs and music of any language.
Phulki.com : It’s a cool search engine for bollywood hindi song lovers. You can search and listen your favorite Hindi music here. Search criteria is quite vast i.e. search can be made using movie, song, singer, star or year etc. Gives quite relevant results.
HindiSongs2.com : Although it cannot be said a search engine. But this is one of my most favorite website when it comes to finding and downloading free Hindi songs. I think all Hindi song fans should boookmark this website.