Dropbox has allowed instant upload for iPhones for quite some time. While the Mac version isn't getting the exact same treatment, it is getting a new import tool for iPhoto users. You can also now choose to automatically save screenshots to your account whenever you take them, according to the Dropbox blog:
Starting today, all the screenshots you take can automatically be saved straight to your Dropbox. And on top of that, Dropbox will also create a link to your screenshot and copy it to your clipboard — so your picture’s instantly good to share.
Basically, just take enable the screenshot feature and Dropbox will automatically upload your screenshots and copy the link for you. No need to use a separate sharing service if you don't want to.
WIth the new iPhoto import tool, you can easily get all your iPhoto events into Dropbox seamlessly. While an importer is a nice added feature, it would probably be more useful if it worked more like automatic uploads does on the iOS version.
If you happen to try either of these features out, let us know what you think in the comments!
Source: Dropbox blog