These are some of the most popular websites for downloading presets. The presets listed here are a mix of PV2012 (Lr4/5) and earlier (PV2010/2003), and I’ve split them into Free vs. Paid to help your search. If you know of any more that you think should be included, please let me know. Enjoy!
Free & Paid Presets
Only Paid Presets
There’s also a long list of less well known presets you might like to explore here too: ProPhotoShow