I committed a rookie error and installed my battery with the leads crossed, ie. Positive to ground, Neg to starter. Ugh, I know. Now bike is dead. Where to start? Volt regulator? Help.

 

Try to install it correctly and see if it starts. (I'm sure you did already)
check the battery
check the starter
check the stator leads to ground to make sure you didn't fry it

 

Depending on what year The bike will should start without the voltage regulator or the stator connected it just won't recharge

 

All electrics on bike are dead, bike is an 01 Sportster.

 

Battery is good, starter is new and verified it is good. But my mistake created new problem
and I'm looking for what is most likely damaged and go from there.

 

Fuses- check all your fuses- especially maxifuse

 

"Maxifuse"? Circuit breaker is good. Is that "maxifuse" in line to the regulator?

 

May be inline from positive terminal at batt and #30 terminal at starter relay. Should be close to battery?
Have you checked all the other fuses in the fuse block?

 

All fuses good, circuit breaker good. Not finding a fuse, only the circuit breaker.

 

Help others to help you.
You have a 2001 sportster what? 883, 1200 USA model?
What condition was bike in prior to problem?
So you attached battery backwards and attempted to start or went down the road with it or what?
What does battery is good mean to you? load tested? just a voltage test?
Why is starter new?
We can not see or touch the bike so from a distance with zero history it is rather difficult to know what you have.
Could be something like a security system that got fried, a relay that got burnt or ignition module was destroyed but from a distance it is rather difficult to direct a solution.