is it possible to find mp3 songs with lyrics?

Only if it's in the comments section of the file. To check, go to the file, right click it, and click properties. After that, it will show a box telling you about the file; click the Summary tab, and it will show a white box. If there's lyrics or any kind of text, it will show you it.
But then again, most people won't put lyrics there. So it's not very common, but yes it is possible; if the uploader chooses to put lyrics.

Off topic, but Woo hoo! 700 posts!

@ cg52965,

Are you talking about karaoke? See: http://www.gnutellaforums.com/audiobook-karaoke-issues/. If you just want the lyrics, then use google.

@ garbagefan2,

Congrats mate ! Only 300 to go .

__________________
If it ain't broke, fix it till it is!

LyricsTextScroller scrolls the text and chord for any lyric. You can also select a mp3 or midi to play together. The software is free but you have to send a e-mail in order to get a license.
LyricsTextScroller for PC

For MacOSX I would recommend both Get Lyrical and TuneLyrics. I work them both together. If neither can get them, then TuneLyrics will help you find them. Sure, not 100% accuracy, but that is something you need to judge, especially by re-listening to the lyrics to be sure they match in those cases where there's some doubt.
With Get Lyrical you can select which songs you wish to check (multiple songs.) I usually check with this one first.