Unfortunately, of all of the artists who covered his work, very few gave him credit, and some actually claim to have wrote the songs themselves. The only exception I know of is Nirvana, who properly credit him with Where Did You Sleep Last Night?, but I'm willing to accept that there are probably others who did that I don't know about. A partial list of artists who posthumously ripped him off follows:

Led Zeppelin: Gallows Pole, originally titled Mama Did You Bring Me Any Silver
AC/DC: Have A Drink On Me, originally titled Have A Whiff On Me, and about cocaine, not alcohol. quote: I walk up Elm and I come down Main; Try to bum me a nickel(!) just to buy cocaine

Johnny Cash: Rock Island Line, Pick A Bale of Cotton and I Got Stripes, originally titled Ain't Gonna Ring Dem Yellow Woman's Do Bells.
Gordon Jenkins and the Weavers, Frank Sinatra and many others: Good Night Irene
Greatful Dead or Jerry Garcia Band: Hesitation Blues, C.C. Rider

This list is by no means complete. I knew 5 of these off the top of my head, the others I scoured the web for. If anyone else can add to it, I hope that they will. What I did is searched for songs from Leadbelly's discography (you can find it at http://www.cycad.com/cgi-bin/Leadbelly/discog/). Then I searched for web sites with the song title and without the names Leadbelly, Ledbelly, Ledbetter, or Huddie. And about .001% of the pages had what I was looking for.