Here are some options:
General Happiness:
* Stoked: Excited and enthusiastic.
* Buzzing: Feeling happy and energetic.
* Chuffed: Pleased and delighted.
* Tickled pink: Very happy and pleased.
* Over the moon: Extremely happy.
* Beaming: Radiating happiness.
More Specific Slang:
* Lit: Having a good time, often with a party or event.
* Pumped: Excited and enthusiastic, often about something upcoming.
* Giddy: Lighthearted and carefree happiness.
* Blissful: Deeply content and happy.
Informal Slang:
* Happy as a clam: Extremely content.
* Feeling good: Generally happy and positive.
* On cloud nine: Feeling extremely happy.
The best word to use will depend on the specific situation and the tone you want to convey.