I found some answers here, but they seem a bit dated (thus I'd argue this isn't a duplicate). Currently, I create a private gallery on my website where I post the finished images, but the website downgrades them to about 90% resolution, and only provides the option to download a low-res sample. The thing I like about the site is that the customer can purchase prints directly from it if they so choose.
I then send the full-res finished images in a USB stick to the customer. I was using Google Drive or Dropbox for a while, but my Google Drive started to fill up and buying more storage seems like a temporary fix until I need more storage again.
So what do you use to share finished images with clients? How about for your own images so that you can easily access them from anywhere and show/share?