There’s also a content server built into Calibre but I’ve never used it.

I use Ubooquity (a Java app with a web interface) that I share books with family and friends using the kindle browser

Edit: Just noticed a ‘wireless device connection’ option in the Connect/Share menu

Connect your ebook device to your PC running Calibre. Start Calibre, and when it recognises your device a new button will show for syncing with the device.

I am using Memmy at the moment and it’s well decent

https://github.com/Memmy-App/memmy