I've spent several years maintaining a giant spreadsheet of all tasty fruit patents to track what's active and what's expired. (see attached link)
Highlights from this year's patent expirations:
Plum 'Emerald Beaut'
Pluot 'Dapple Dandy'
Nectarine 'Liz's Late'
Nectarine 'Honey Kist'
Nectarine 'Arctic Star/Gold/Sweet'
Peach 'Zee Diamond'
Avocado varieties 'Sir-Prize', 'Lamb Hass' and 'Fruta De Oro'
Disclaimer: I am not a lawyer. I'm pretty sure my table is correct but there may be errors in my data. Check with a real lawyer before taking on any major propagation efforts with potentially patented material.