Here are a few good lists of authors on Twitter:
Literary Tweets: 100+ of the Best Authors on Twitter
Nonfiction Tweets: 70+ Authors to Follow on Twitter
Felicia Day’s Twitter Author List
Some of the authors I follow @52projects:
@kevinsampsell
@larrysmith
@jenniferperkins
@jamiattenberg
@hollylecraw
@sisterdiane
@kwohlrob
@craftychica
@craftivista