I recently needed to get a few photos (the "specking out" snapshots of Sam flying with Ben) from a borrowed computer to my phone. I searched for a number of free services, and I was generally unsatisfied with them. Then I came across tempsend.com. The site is very simple with no ads or frills. But it seemed to work fine. You just click "Choose File" to navigate to your file, choose how long they should keep it, and click Upload. They give you a randomized URL that you can use to download it to another computer anywhere.
I've only used the site one time, so this is not an unconditional endorsement. But I can say that my experience was good.