General synonyms:
* Quickly
* Rapidly
* Speedily
* Expeditiously
* Hastily
* Immediately
* Pronto
* In a flash
* With alacrity
* At a rapid pace
More specific synonyms:
* For movement: hurriedly, briskly, nimbly, fleetly
* For action: promptly, speedily, readily, efficiently
The best synonym to use will depend on the specific context of your sentence.