I grew up with old-school country, so I've been a Johnny Cash fan for 30 years or so. If you like him, you should check out the following:
Willie Nelson
Merle Haggard
George Jones
Waylon Jennings
Shooter Jennings
Kris Kristofferson
Marty Robbins
Glen Campbell
Wanda Jackson
Patsy Cline
Dolly Parton
Loretta Lynn
Emmylou Harris
Tammy Wynette
Donna Fargo
Conway Twitty
Jerry Reed
Hank Williams
Hank Williams, Jr.
Hank III
Buck Owens
Carl Perkins
Charlie Daniels
Charlie Rich
Charley Pride
Ray Price
Tom T. Hall
Alabama
The Statler Brothers
Roy Acuff
Roger Miller
Bob Wills and His Texas Playboys
Old Crow Medicine Show
Slim Whitman
Mel Tillis
Mickey Gilley
Ronnie Milsap
Eddie Rabbit
John Denver
Kenny Rogers
Johnny Cash also recorded with Bob Dylan. They collaborated during the time Bob was recording Nashville Skyline. Elvis Costello's new album Secret, Profane and Sugarcane has a definite country feel to it.