Yeah. He started out solo as part of Ice-T's Rhyme Syndicate click(remember that?). Put out an album in 1990 or something. "I Got The Knack" was a pretty big single. Then they had a falling out or something, really I can't speak cause I don't know too well, and he came back with House of Pain (wich were all Irish). Put out some successful albums and cla**ic tracks that became mainstream hits (especially Jump Around, also that Boom Shalack Lack Boom song, however it was spelled).
Then after a few years, they lost their DJ (DJ Lethal) to Limp Bizkit. Everlast dissappeared again for few years. Came back solo, but this time he wasn't only an MC; he also did blues. He had a few song that were well received outside of hip-hop circles (Then You Really Might Know What It's Like, Ends, etc.) and continued mc'ing. Did have a small beef with Eminem over some particularly silly shit. Nowadays, I think he raps less and less and does his blues thing more and more.
That's what I know.