As compared to photoshop brushes there are not enough free brushes available for illustrator. It is very hard to find the quality illustrator brushes, but i searched the internet for best and quality illustrator brushes and compiled a list.
Here i have collected free exclusive & colorful Illustrator brushes, i hope these brushes will be helpful for you.
Exclusive Illustrator Watercolor Brushes
60 brushes for Illustrator
100 Wonderful Water Color Illustrator Brushes
Fresh Brushes by *mikomi26