Great West Casualty: one of the largest players
Progressive: one of the largest players, new trucking companies are welcome, will penalize you for drivers' tickets.
Crum & Forrester
Northland
Sentry
Lancer
Aegis
Amtrust
Auto Owners
Canal
Falls Lake
Nationwide
Occidental
United Specialty
Trisura
Knight Specialty (good choice for new companies)