I don’t do this every year, but in past years I’ve picked a few of my favorite free products or services and donated to them.
Let’s Encrypt – Free SSL certificates. This is game changing when you manage a lot of web sites, including numerous subdomains.
HeidiSQL – An easy to use, portable Windows application that lets you manage remote databases.
FastStone Image Viewer – I’ve used the portable version for years. It’s fast and has a ton of features (including cropping and batch resizing, to name a few).
There are thousands of high quality and useful free services and software. But I’ve learned through sad experience that if you don’t donate, they may cease to exist in a few years. If you don’t want that to happen to your favorites, consider a donation.