Hundreds of carrot varieties exist, There are four primary groups
Imperator ,Nantes ,Danvers ,Chantenay {Carrot Seeds}
The following are my personal favorites, you of course may prefer to scan any of the many online nurseries and seed catalogs for the varieties of Carrots you'd prefer to grow.
Baby Spike: Matures in 50 days, 3- to 4-inch Baby carrot holds its shape . It remains sweet and petite well past maturity. An excellent variety of Carrot for snacking.
Bolero: Matures in 72 days. Nantes-type carrot resistance to many diseases and stores well.
Rainbow Carrot : Is actually a blend of various seeds sold by Hirtsin a variety, as implied by the name, in various colors and shapes. Several other nurseries also have similar blends of carrot varieties.
Imperator: Matures in 70 days. Imperator-type variety is long and narrow and has a deep orange color. .
Short N Sweet Carrot: Matures in 68 days. Four-inch Chantenay-type carrot grows well in heavy clay soil. This carrot variety is very similar to supermarket varieties of carrots