General:
* Active
* Operational
* Functional
* Working
* InUse (this is a bit more technical, but it's accurate)
* Engaged (for things like tools or resources)
* Utilized
More specific:
* Running (for machines or systems)
* Employed (for strategies, methods, or people)
* Deployed (for software or systems)
* Activated (for features or tools)
Informal:
* Going
* Live
* Up and running
The best word to use will depend on the specific context.
For example:
* "The new software is active and ready for use."
* "The old system is operational but will be replaced soon."
* "We're employing a new marketing strategy this quarter."
Can you give me more context about what you're trying to say? This would help me give you a more accurate recommendation.