Other than curls what's the best workout for biceps?
There are several ways you can get creative in your bicep development in addition to traditional curls that you would usually do with a barbell or by using dumbbells.
Any type of pulling movement will recruit your biceps to some degree especially when performing chin-ups or pull-ups. For example, strict chin-ups will help develop your biceps but you can enhance bicep recruitment by performing a slow decline (8–10 seconds) from the top. Performing an isometric hold half way down will also stimulate your biceps muscle.
You can perform what is called "head bangers" on a pull up bar. This will require enough upper strength to sustain your body weight while performing the exercise so it's considered an advanced level exercise. You stop half way down when doing a pull-up and when your arms are at a 90 degree angle, you move back and forth laterally as if your constantly banging your head against the bar. I demonstrate them here during a full body routine: