If your parents left behind things you don't really need in your daily life, why not put them to good use? You can sell those items on craigslist, ebay or if it's funky enough, even etsy! Put money from the sales in a special envelope. You can write something on it like "love mom and dad" or just leave it blank. Maybe even draw a big heart on it! When everyone is getting presents from their parents or you're just feeling like you'd like a physical gift from them - buy yourself something using the money in the envelope! The gift will be from the your parents and you will be able to use it or appreciate it even more.
If you are trying to maximize the amount of money you have on hand to buy yourself presents, I would *not* recommend having a yard sale. You don't make a ton of money off of yard sales, the whole point is really just to get rid of stuff. Another blog post for another time...
A little story about my envelope
After 3 years, we finally sold my mom's beetle. I split the money with my brother. I have an envelope that I keep money in and when I'm feeling down or missing my mom (she used to buy me a lot of gifts), I can buy myself a present! This feels like I'm keeping the memory of my mom giving me gifts alive, and I can rid of things I'll never use just because I'm emotionally attached to them.
I've bought myself a couch from old stuff my parents left behind, clothes, entertainment. When I run out of money in the envelope, I find something else to sell. I feel like they left behind so much, this is a good opportunity to turn things I don't use into treasures I will use.