Sure, here are some popular free slot games you can play just for fun:
1. **Starburst** - A vibrant and colorful slot game with a space theme.
2. **Gonzo's Quest** - Join Gonzo on his quest for gold with this adventure-themed slot.
3. **Cleopatra** - Experience the ancient Egyptian theme with this classic slot.
4. **Book of Ra** - Another Egyptian-themed slot that's very popular.
5. **Mega Moolah** - Known for its progressive jackpots, but you can play a free version too.
6. **Buffalo** - A popular slot with a North American wildlife theme.
Most online casinos offer a demo mode where you can play these games without wagering real money. Have fun!