Droplr is free and easy way to share images, documents and other files. You can run it from a web browser or the Mac app which lives in your menu bar. To share a file, simply drag it onto the menu bar item and it's uploaded to Droplr's servers. When the upload is complete, it copies a short URL to your Mac's clipboard, which you can give to anyone you like.
There is a 25 MB upload limit for individual files, and storage is free up to 1 GB. There is a paid plan in the works, but no details are being offered yet. The app also supports plug-ins so you can quickly share from apps like iPhoto, Photoshop CS5, Firefox, Safari, Google Chrome, your address book and even PhotoBooth.
Things I'd like to see include a favorites list of contacts for sending files so I don't have to go through pasting the URL into mail, and I think the 25 MB file size limit is too low. I have some Photoshop files that easily exceed that.
There are some similarities to Dropbox, another excellent file sharing utility that gives you 2 GB for free and doesn't limit individual file size. On the other hand, Droplr is simpler to use and aimed primarily at sharing with other people. Dropbox can be used to share files, of course, but is more about storage and sharing across machines.
Droplr offers support for Windows machines and has an iOS app in development. Of course any computer can use it via the web, with no app needed.
I've had no problems with using Droplr, and when I asked a question at the support site it was instantly answered. If you like to share files, give Droplr a look. It will be interesting to see how the service progresses and improves.