SMW Central is the main website for all of your YI (and SMW) romhacking needs. They host a large library of completed hacks as well as everything you'll need to create your own! Keep in mind that not every YI hack that exists is on the SMW Central hack list (e.g. single level hacks). We'll try our best to do that here:
- SMWC Yoshi's Island romhack list. 
- Level design contest 1 
- Level design contest 2 
- Level design contest 3 
- Miscellaneous hacks 
1. Select "Apply Patch".
2. Select the patch that you want to use (IPS or BPS file) and click "Open".
3. Select an unmodified, 1.0 (U) ROM of Yoshi's Island and click "Open".
4. Click "Save" (or rename the ROM if you want to).
5. Open the patched ROM in an emulator and enjoy!