I love Droplr, and over the last six months I have used it nearly 800 times. It’s one of the very few online services that I pay actual money for (I used to pay for LastPass, but I switched to 1Password, which is slightly better for my needs and has a one-time fee).
One of Droplr’s best features, just released, is that in many apps you can share the current version of your document, image, or video just by hitting a keyboard shortcut. That means I can quickly send a design client four variations on his logo (see image below) by switching back and forth directly from Photoshop to Gmail. Alt+D shares the current state of the PSD as a PNG, and the share URL is automatically put on my clipboard. Then I get over to Gmail and paste the link in the message. Awesome.
I also use Droplr to save little snippets of text for my own use: take a quick screenshot of the two phone numbers you’re going need next Thursday, paste the URL into a QuickCal dialog to put it in your Reminders list, and there they are next Thursday when you need them. I share passwords with Droplr via a screenshot, and then inform the recipient that I’ll be deleting the image in ten minutes. Screenshots are easily annotated, too.
This blog post explains the way Droplr distinguishes itself from Dropbox (I use and love both services). They’re running a sale right now, and if you use my affiliate link we both save on the service. If you’re a designer—or if you frequently send files of any size or kind—Droplr is for you.